LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 


Class 


raffi 


1  ,  m  . 


-  * 

•;--  HI 


THE 

CYANIDE   INDUSTRY 

THEORETICALLY  AND  PRACTICALLY 
CONSIDERED 


BY 

E.    EOBINE      -  M.    LENGLEN 

CHEMICAL  ENGINEER  CHEMICAL  ENGINEER 

Graduate  of  the  School  of  Physics  and  "iomreat"  of  the  Conservatoire  National 
Chemistry  of  the  City  of  Paris  des  Arts  et  Metiers 

and  of  the  Pasteur  Institute  Director  of  Works 


TRANSLATED  BY 

j.  ARTHUR  LECLERC 

PH.D.,  UNIV.  HALLE-WITTKMBERG 

Physiological  Chemist,  Bureau  of  Chemistry,  Department  of  Agriculture 
Washington,  D.  C. 


WITH  AN  APPENDIX  BY  C.  E.  MUNROE,  Pn.D 


FIRST    EDITION 

FIRST   THOUSAND 
^ 

UNIVERSITY 

OF 

NEW   YORK 

JOHN  WILEY   &   SONS 
:   CHAPMAN   &    HALL,    LIMITED 
1906 


Copyright,  1906 
BY 

j.  ARTHUR  LECLEBO 


ROBERT   DRUMMOND,   PRINTRR,   NKW  YORK 


TRANSLATOR'S  PREFACE. 


THE  publication  of  Robine  and  Lenglen's  "L'lndustrie  des 
Cyanures"  in  the  series  Encyclopedic  Industrielle  in  France  is  a 
good  indication  of  the  value  of  the  work. 

The  translation  of  this  book  into  English  makes  more  accessible 
to  the  American  worker  in  Industrial  Chemistry  the  many  and 
various  processes  proposed  for  the  production  of  cyanide  compounds, 
and  should  be  a  help  in  stirring  him  to  greater  endeavor  along 
these  lines. 

The  Index,  rarely  found  in  French  books,  has  been  added  by 
the  translator,  and  at  his  suggestion  the  publishers  have  appended 
Dr.  Chas.  E.  Munroe's  brochure  on  "  Precious  Metals  Recovered  by 
Cyanide  Processes"  which  recently  appeared  as  a  publication  of  the 
U.  S.  Dept.  of  Commerce  and  Labor. 

The  translator,  being  moreover  interested  in  Agricultural  Chem- 
istry, dares  to  hope  that  one  of  the  results  of  this  translation  will 
be  the  successful  fixation  of  atmospheric  nitrogen  on  an  industrial 
scale. 

WASHINGTON,  January,  1906. 

iii 


TABLE  OF  CONTENTS. 


PAG 

INTRODUCTION 


PART  ONE. 
CHEMISTRY  OF  CYANOGEN  AND  ITS  DERIVATIVES. 

CHAPTER  I. 
GENERAL  CONSIDERATIONS  .....................  . 

CHAPTER  II. 


PHYSICAL  AND  CHEMICAL  STUDY  OF  CYANOGEN  AND  ITS  DERIVATIVES  ......  10 

Cyanogen.  .:  ...................................................  .  10 

Paracyanogen  ...................................................  13 

Hydrocyanic  Acid  ...............................................  14 

Metallic  Cyanides  .....  ...........................................  18 

Potassium  Cyanide  .........................................  20 

Sodium  Cyanide  ...........................................  23 

Ammonium  Cyanide  .......................................  23- 

Calcium  Cyanide  ...........................................  24 

Barium  Cyanide  ...........................................  24 

Aluminium  Cyanide  ...................................  .....  24 

Iron  Cyanide  ...........................................  ...  25 

Chromium  Cyanide  ..........................  ..............  25 

Manganese  Cyanide  ........................................  25 

Tin  Cyanide  ...............................................  25 

Lead  Cyanide  .............................................  25- 

Copper  Cyanide  ...........................................  26 

Mercury  Cyanide  ..........................................  26; 

Silver  Cyanide  .............................................  26 

Cobalt  Cyanide  ............................  .  ...............  27 

Nickel  Cyanide  ......................  .  .....................  27 

Gold  Cyanide  .............................................  27 

Platinum  Cyanide  .............  ............................  27 

Double  Cyanides  .................................................  28 

Ferrocyanides.     Potassium  Ferrocyanide  .....................  29 

Ferricyanides  .............................................  32 

v 


TABLE  OF  CONTENTS 

PAGE 

Cobalticyanides 34 

Manganocyanides.  .  „ 34 

Platinocyanides 34 

Aurocyanides 35 

/     Nitroprussiates 35 

Oxygen  Compounds  of  Cyanogen 36 

\s  Cyanic  Acid 36 

Potassium  Cyanate 36 

Cyanuric  Acid  and  Tricyanates 37 

Sulphocyanides 37 

Potassium  Sulphocyanide 38 

Organic  Compounds 39 

,   Nitriles  and  Carbylamines 39 

v  Cyanic  Esters 40 


CHAPTER  III. 

OENERAL  PROPERTIES  AND  METHODS  OF  DETERMINATION  OP  THE  VARIOUS 

CYANIDE  COMPOUNDS 42 

I.  Analytical  Properties 42 

Hydrocyanic  Acid 42 

Cyanides.  .  . 42 

Ferrocyanides 43 

Ferricyanides 43 

Sulphocyanides 43 

Cyanates 44 

II.  Methods  for  the  Analysis  of  the  Various  Cyanide  Compounds. .  44 

Cyanides 44 

Liebig's  Method 44 

Fordos  and  Gelis'  Method 45 

Analysis  of  Commercial  Potassium  Cyanide 47 

O.  Hertig's  Process 47 

Determination   of   Medicinal   Hydrocyanic   Acid   in  Dis- 
tillates of  Bitter  Almonds  and  Laurel  Cherry  (Bui- 

gnet  Method) 48 

Ferrocyanides 49 

Sulphocyanides 50 

Determination  of  Ferrocyanides  in  the  Purifying  Materials  of 

Illuminating-gas » 50 

Knublauch's  Method 50 

Moldenhauer  and  Leybold's  Method. 51 

Burschell's  Method ^ 52 

Zaloziecki's  Method 52 

Donath  and  Margosches'  Method. 53 

Determination  of  Prussian  Blue  in  the  Spent  Oxids 54 

Method  of  Nauss  of  the  Carlsruhe  Gas  Works 54 

Toxicological  Research 54 


TABLE  OF  CONTENTS.  vii 


CHAPTER  IV. 

PAGE 

THERMOCHEMICAL  DATA  OF  THE  CYANIDE  COMPOUNDS 56 

I.  Cyanogen 56 

II.  Hydrocyanic  Acid 57 

III.  Potassium  Cyanide 58 

IV.  Ammonium  Cyanhydrate 60 

V.  Potassium  Ferrocyanide . .  ."T 60 

VI.  Potassium  Cyanate 66 


PART   TWO. 
PRESENT  CONDITION  OF  THE  CYANIDE  INDUSTRY. 

CHAPTER  V. 
COMMERCIAL  AND  INDUSTRIAL  STUDY 


PART  THREE. 

METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

GENERAL  CONSIDERATIONS 81 

CHAPTER  VI. 

MANUFACTURE  OF  CYANIDES 85 

I.  Non-synthetic  Processes 85 

A.  Extraction  of  Cyanides  from  Ferrocyanides 85 

Old  Process 85 

Liebig's  Process 87 

Wagner's  Process .88 

Chaster' s  Process 88 

Rossler  and  Hasslacher's  Process 89 

Wichmann  and  Vautin's  Process 90 

Dalinot's  Process 92 

Adler's  Process 93 

Etard's  Process .' . .  94 

Bergmann's  Process 94 

B.  Extraction  of  Cyanides  from  Sulphocyanides 95 

I.  By  Oxidation 96 

Raschen's  Process 97 

Beringer's  Process 101 

II.  By  Reduction 102 

Playfair's  Process 102 


viii  TABLE   OF  CONTENTS. 

PAGE 

Hans  Luttke's  Process. . . , 104 

British  Cyanide  Co.'s  Process 105 

Hetherington  and  Musspratt's  Process 106 

Process  of  the  Silesia  Verein  Chemische  Fabrik.  .  .  .    107 

Goerlich  and  Wichmann's  Process 107 

Bower's  Process 107 

Conroy's  Process 108 

Rasfchen,  Davidson,  and  Brock's  Process 110 

Etard's  Process 110 

Finlay's  Process 110 

II    Synthetic  Processes — General  Remarks Ill 

A.  Processes  Utilizing  Atmospheric  Nitrogen 117 

Bunsen's  Process 123 

Possoz  and  Boissiere' s  Process 124 

Newton's  Process 126 

Blair's  Process 126 

Armengaud's  Process! 126 

Marguerite  and  Sourdeval's  Process 126 

Mond's  Process.  . 127 

Weldon's  Process 128 

Fogarty's  Process 128 

Dickson's  Process 129 

Lambilly's  Process 129 

Gilmour's  Process 134 

Young's  Process.  .  . 134 

Mackey's  Process 135 

Readmann's  Process 135 

Mehner's  Process 137 

Swan  and  Kendall's  Process 137 

Pestchow's  Process 137 

Chipmann's  Process 138 

Moi'se  and  Mehner's  Process 140 

Castner's  Process 141 

Hornig  and  Schneider's  Process 143 

Mehner's  Process 143 

Frank  and  Caro's  Process 144 

Process  of  the  Chemische  Fabrik  Pfersee,  Augsburg 149 

Berniger,  Wolfram  and  Blackmore's  Process 150 

Dziuk's  Process 1 50 

Process  of  the  General  Electro-Chemical  Co 152 

B.  Processes  Utilizing  Ammonia 1 53 

Lance  and  Bourgade's  Process 156 

Mactear's  Process 157 

Stassfurter  Chemische  Fabrik' s  Process 158 

Moulis  and  Sar's  Process 160 

Lambilly's  Process 161 

Beilby's  Process 162 

Young  and  Macfarlane's  Process 1 63 


TABLE  OF  CONTENTS.  ix 

PAGE 

Chaster' s  Process 165 

Pleger's  Process 165 

Roca's  Process.  ^ 166 

Hood  and  Salamon's  Process 169 

Hornig's  Process 170 

Schneider's  Process 171 

Castner's  Process 172 

Process  of  the  Deutsche  Gold  u.  Silber  Sheide  Anstalt 175 

Lambilly's  Process 178 

Martin's  Process. 179 

Clock's  Process 179 

Huntington's  Process 180 

Hoyermann's  Process 180 

Roussin  Process 181 

Kerp's  Process 181 

Kellner's  Process 182 

Grossmann's  Process 182 

III.  Special  Processes 183 

Process  of  the  Chemische  Fabrik  Aktiengesellschaft 183 

Vidal's  Process 184 

Bueb's  Process 185. 

Ortlieb  and  Miiller's  Process .170 


CHAPTER  VII. 

MANUFACTURE  OF  FERROCYANIDES 192 

I.  Old  Processes,  Based  on  the  Use  of  Nitrogenous  Organic  Substances  193 

Calcination  or  Production  of  Metal : 197 

Engler's  Apparatus .  201 

Theory  of  the  Manufacture  of  Ferrocyanide  of  Potassium  by  the 

Old  Process. 205 

Yield 207 

Lixiviation  and  Crystallization 210 

BrunquelPs  Process 210 

Karmrodt's  Process 211 

Conroy's  Process 212 

Musspratt's  Process 212 

Goerlich  and  Wichmann's  Process 213 

Process  of  the  Castelet  Works 213 

II.  Extraction  of  Cyanide  Compounds  from  Illuminating-gas  and  its 

Residues 214 

A.  Direct  Extraction  from  Gas 229 

Knublauch's  Process 231 

Gasch's  Process 232 

Rowland's  Process 233 

Fowlis'  Process 233 

Clauss  and  Domeier's  Process 234 

Schroeder's  Process.  .  234 


X  TABLE  OF  CONTENTS. 

PAGE 

Teichmann's  Process 235 

Lewis'  Process 236 

Bueb  Process 237 

Feld's  process 241 

B.  Extraction  of  Cyanogen  Compounds  from  the  Ammoniacal 
Liquors 242 

Pendrie's  Process 242 

Bower's  Process 243 

Lewis'  Process 243 

C.  Extraction    of    Cyanogen    Compounds    from    the    Purifying 
Materials 245 

Gauthier-Bouchard's  Process 248 

Valentin's  Process 256 

Harcourt's  Process 257 

Kunheim's  Process 257 

Hempel's  Process 257 

Wolfram's  Process 257 

Donath's  Process 258 

Richter's  Process 258 

Esop's  Process 258 

Marasse's  Process 258 

Holbling's  Process 259 

Lewis'  Process 259 

Mascow's  Process 259 

/ 
CHAPTER  VIII. 

MANUFACTURE  OF  FERRICYANIDES 261 

The  Chlorine  Process.  .  .  i 261 

Reichardt's  Process 263 

Process  of  the  Bouxvillers  Mines 264 

Dubosc's  Process 265 

Process  of  the  Deutsche  Gold  und  Silber  Sheide  Anstalt 265 

Kassner's  Process. 266 

Carl  Beck's  Process 267 

Williamson's  Process 267 


CHAPTER  IX. 

MANUFACTURE  OF  SULPHOCYANIDES. 269 

Geli's  Process 270 

Deiss  and  Monnier's  Process 281 

Hood  and  Salamon's  Process 282 

Brock's  Process 282 

British  Cyanides  Co.'s  Process \ 283 

Albright's  Process 285 

Tcherniac  Process 285 

Goerlich  and  Wichmann's  Process 286 


TABLE  OF  CONTENTS.  xi 


CHAPTER  X 

PAGE 

MANUFACTURE  OF  PRUSSIAN  BLUE  AND  VARIOUS  OTHER  COMPOUNDS 288 

Soluble  Prussian  Blue 292 

Turnbull's  Blue 292 

Monthier's  Blue  or  Ammoniacal  Prussian  Blue 292 

Antimony  Blue 293 


PART   FOUR. 
THE   USE  OF  CYANOGEN  COMPOUNDS. 

CONCLUSIONS 321 

TABLES  AND  DATA 323 

APPENDIX:  DIGEST  OF  U.  S.  PATENTS  RELATING  TO  CYANIDE  PROCESSES  FOR 

THE  RECOVERY  OF  PRECIOUS  METALS 331 

INDEX 403 


THE  CYANIDE  INDUSTRY. 


INTRODUCTION. 

Chemical  industries  are  in  a  high  degree  artificial  and  progressive. 

(BERTHELOT:   Opening  speech  at  the  International  Congress 
of  Chemistry,  Paris,  1900.) 

IF  the  condition  of  chemical  industry  at  the  beginning  and  at 
the  end  of  the  nineteenth  century  be  compared,  one  is  immediately 
impressed  with  the  immense  progress  which  has  been  accomplished. 

Chemical  industry,  at  the  beginning,  being  for  the  most  part 
based  on  a  more  or  less  crude  empiricism,  could  not  hope  for  better 
results  than  those  brought  about  either  through  accident  or  through 
long  experience. 

Gradually,  the  rational  study  of  reactions,  and  the  adaptation 
of  purely  scientific  ideas  and  discoveries  to  manufacturing,  made 
it  necessary  to  have,  as  the  basis  of  each  modus  operandi,  a  pro- 
found theoretical  knowledge.  From  that  moment  advance  in 
industrial  chemistry  was  rapid  and  to-day,  also,  it  is  intimately 
bound  to  the  progress  of  scientific  research;  it  is  the  immediate 
result  of  it. 

Among  the  scientific  discoveries  which  have  had  a  great  effect 
on  the  progress  of  industrial  chemistry,  those  which  especially  relate 
to  the  synthesis  of  bodies  should  be  mentioned.  It  is,  in  fact,  due 
to  synthesis  that  numerous  compounds,  which,  till  then,  nature 
alone  was  thought  capable  of  producing,  have  been  successfully 
reproduced.  The  processes  for  the  manufacture  of  certain  products 
have  been  greatly  simplified,  and  consequently  the  net  cost  con- 
siderably reduced  through  the  industrial  adaptation  of  this  principle. 


2  THE  CYANIDE  INDUSTRY. 

The  cyanide  industry,  which  is  to  be  studied  in  this  work,  has 
not  escaped  this  general  law. 

The  happy  discovery  of  Scheele,  who  was  the  first  to  obtain 
Prussian  blue,  was  the  starting-point  of  this  industry.  Later,  potas- 
sium ferrocyanide  was  prepared  by  the  calcination  of  nitrogenous 
materials  in  the  presence  of  alkali  carbonates,  and  although  this 
modus  operand!  was  absolutely  empirical,  it  sufficed,  for  a  long 
time,  for  the  limited  demand.  It  is  probable  that  this  state  of 
affairs  would  have  existed  even  to-day  had  not  the  use  of  potassium 
cyanide  in  the  metallurgy  of  gold  given  to  this  industry  such  an 
impetus  that  the  manufacture  of  cyanide  compounds  has  made 
remarkably  rapid  development. 

The  application  of  cyanides  to  the  treatment  of  auriferous  mate- 
rials, which  dates  bacjc  about  fifteen  years,  is  therefore  the  imme- 
diate .cause  of  the  progress  realized.  Foreseeing  the  great  role  the 
new  industry  was  to  play,  manufacturers  and  investigators  eagerly 
sought  out  every  improvement  possible. 

It  should,  however,  be  stated  that  long  before  not  altogether 
successful  attempts  had  been  made  to  modify  the  old  processes. 

In  the  mean  time,  the  discovery  of  cyanide  compounds  in  the 
purifying  materials  used  in  the  manufacture  of  illuminating-gas 
had  likewise  opened  up  the  field  of  investigation  toward  synthetic 
processes,  but  only  in  individual  cases,  although  very  interesting 
in  themselves. 

The  early  investigations  were  unquestionably  valuable,  and 
those  which  relate  particularly  to  synthetic  production  were  the 
starting-point  for  many  researches.  This  is  the  tendency  of  the 
times;  and  either  in  the  hope  of  a  simpler  manufacture  or  of  approach- 
ing as  close  as  possible  to  the  theoretical  side  of  the  question,  we 
shall  see  that  the  synthetic  processes  for  the  manufacture  of  cyanides 
are  now  preeminent.  These  are  the  processes  which  in  all  proba- 
bility should  produce  the  best  results,  and  should  solve  the  prob- 
lem satisfactorily  from  an  economical  as  well  as  an  industrial  point 
of  view. 

The  study  of  this  special  field  of  industrial  chemistry  is  there- 
fore of  great  interest.  Having  been  occupied  for  many  years  with 
the  different  questions  relating  thereto,  we  find  no  special  works 
on  this  subject,  at  least  in  France. 


INTRODUCTION.  3 

These  reasons  led  us  to  bring  together  in  an  appropriate  didactic 
order  all  the  documents  on  this  subject  which  we  have  been  able 
to  collect  in  the  course  of  our  researches;  such  is  the  genesis  of  the 
work  which  we  present  to  the  public. 

The  work  divides  itself  into  four  parts: 
Part     I.  Chemistry  of  cyanogen  and  its  derivatives. 
Part    II.  The  present  condition  of  the  cyanide  industry. — Com- 
mercial and  industrial  study. 

Part  III.  Methods  for  the  manufacture  of  cyanide  compounds. 
Part  IV.  Application  of  the  various  cyanide  compounds. 


PART  ONE. 

THE  CHEMISTRY  OF  CYANOGEN  AND  ITS 
DERIVATIVES. 


CHAPTER  I. 
GENERAL    LAWS. 

BY  cyanogen  combinations  is  meant  all  compounds  containing 
the  radical  CN. 

This  radical  is  derived  from  several  sources.  It  may  arise  from 
the  direct  union  of  carbon  .and  of  nitrogen,  which  union  produces 
cyanogen  CN;  or  it  may  arise  by  addition  or  substitution  from 
compounds,  such  as  amides,  imides,  or  amines,  whose  real  radical 
is  C  or  CO. 

The  radical  CN  may  therefore  be  related  to  two  classes  of  com- 
pounds: first,  to  true  cyanogen  compounds;  second,  to  isomers  of 
the  first  class,  which  isomers  contain  the  same  elements  in  quan- 
titative proportions;  the  former  differ,  however,  from  the  latter 
from  the  point  of  view  of  their  chemical  constitution,  and  are 
endowed  with  different  and  peculiar  properties. 

The  formation  of  cyanogen  and  of  its  derivatives,  its  constitu- 
tion and  the  determination  of  its  valency  have  all  been  the  object  of 
much  research,  and  although  these  various  points  have  not  yet  been 
definitely  solved,  the  results  of  these  various  studies  allow  the  question 
to  be  thus  considered:  Carbon,  a  tetratomic  element,  is  saturated 
by  means  of  the  free  nitrogen  valencies.-  This  latter  is  sometimes 
triatomic,  and  sometimes  pentatomic.  In  the  latter  case  three  of  its 


GENERAL  LAWS.  5 

valencies  are  different  from  the  other  two.  It  follows  that  the  carbon 
may  therefore  satisfy  three  of  its  valencies;  the  compound  thus 
formed  will  have  three  free  bonds,  one  attached  to  the  carbon  and  two 
to  the  nitrogen.  The  constitution  of  cyanogen  may  therefore,  from 
these  considerations,  be  represented  by  the  formula  -C=N  =  . 

This  constitution  of  cyanogen  allows  some  of  its  properties  to 
be  at  once  foreseen.  If  the  nitrogen  be  replaced  by  elements  of 
the  same  atomic  value,  the  original  compound  becomes  transformed 
into  a  more  carbonaceous  one.  On  the  other  hand,  if  the  radical  CN 
is  connected  with  an  alcoholic  radical,  the  union  takes  place  through 
the  carbon  atom.  Moreover,  Gautier,  Wurtz,  Limpricht,  and  Cloez 
admit  that  cyanogen  is  trivalent,  for  they  succeeded  in  forming 
the  union  of  hydrocyanic  acid  and  of  its  esters  with  the  haloid 
acids.  The  question  of  the  formation  of  cyanogen  and  its  com- 
pounds is  far  from  being  solved.  It  has  been  the  object  of  much 
dispute,  and  deep  study  has  not  given  sanction  to  one  theory  more 
than  to  another. 

The  various  methods  by  which  this  formation  may  be  explained 
are  based,  rather,  on  probabilities  than  upon  real  data  and  an  exact 
knowledge  of  the  phenomena  produced. 

Nevertheless,  this  question  is  worthy  of  attention  from  more 
than  one  point  of  view.  No  doubt  the  discovery  of  the  true  method 
of  the  formation  of  the  cyanogen  compounds  would  bring  about, 
as  an  immediate  result,  the  proper  process  of  manufacturing  these 
same  compounds.  Therefore  it  may  not  be  useless,  at  the  beginning 
of  this  work,  to  give  some  idea  of  the  theory  of  "  cyanides,"  and, 
without  attempting  to  establish  it  in  a  definite  manner,  to  give 
the  pros  and  cons  of  each  of  the  theories  propounded. 

It  is  known  that  the  radical  CN  cannot  be  formed  through  a 
direct  union;  it  is  formed,  however,  whenever  C  and  N  are  found 
in  the  presence  of  an  alkali  at  a  high  temperature:  then  there  is 
formed  a  cyanogen  compound  in  which  the  group  CN  is  found 
united  to  the  alkali  metal.  This  reaction  takes  place  according 
to  the  general  formula 

C+N+M  =  CNM. 

This  reaction,  or  rather  the  formation  of  the  group  CN,  may 
be  explained  in  several  ways;  in  favor  of  each  theory  strong  but 


6  THE  CHEMISTRY  OF  CYANOGEN. 

refutable  argument  may  be  presented.     The  various  ways  of  con- 
sidering the  subject  will  be  treated  in  order. 

Let  us  take,  for  example,  cyanide  of  potassium  composed  of 
the  three  elements 

C,  N,  K, 

the  union  of  which  will  give  the  final  product  CNK,  and  let  us  see 
under  which  conditions  this  product  may  be  formed. 

Three  hypotheses  are  put  forth  in  explaining  this  formation. 

(1)  In  the  presence  of  the  alkali  metal  the  carbon  unites  with 
the  nitrogen  to  form  cyanogen  CN,   which,  reacting  on  the  alkali 
metal  as  fast  as  it  is  formed,  would  give  the  cyanide  of  this  metal 
as  end  reaction 

(2)  The  nitrogen  unites  with  the  alkali  metal  to  form  a  nitride, 
which  in  contact  with  carbon  becomes  transformed  into  cyanide. 

(3)  First,  there  is  a  union  of  carbon  and  potassium,  forming  a 
carbide,  with  which  nitrogen  reacts  to  produce  cyanide. 

The  first  thing  noted  in  these  three  hypotheses  is  that  in  each 
case  the  final  combination  takes  place  only  after  an  intermediary 
reaction,  and  that  the  fixation  of  nitrogen  cannot  take  place  with- 
out this  intermediate  agent,  the  nature  of  which  is  still  undeter- 
mined. The  first  hypothesis  is  supported  by  the  following  facts: 
When  cyanide  of  potassium  is  prepared  by  heating  nitrogenous 
animal  matter  with  an  alkali  carbonate,  it  is  noticed  that  the  for- 
mation of  the  cyanide  takes  place  only  at  a  temperature  in  the 
neighborhood  of  which  the  alkali  carbonate  is  reduced  to  a  metallic 
state.  Therefore  the  combination  C  +  N  is  due  to  the  presence  of 
the  alkali  metal. 

Schuetzenberger,  among  others,  puts  forth  the  theory  that  at 
the  temperature  of  the  experiment  the  carbon  tends  to  become 
separated  from  the  alkali  with  which  it  is  combined. 

Moreover,  if  a  current  of  free  nitrogen  or  of  ammonia  be  passed 
over  a  mixture  of  alkali  carbonate  and  charcoal  heated  to  bright 
redness,  there  is  formation  of  cyanide.  The  same  result  is  obtained 
if  nitrogenous  matter  be  heated  in  the  presence  of  potassium  or 
sodium.  All  these  facts  would  seem,  therefore,  to  prove  that  the 
presence  of  an  alkali  metal  is  necessary  to  effect  the  union  of  car- 
bon with  nitrogen.  Another  corroboration  of  these  observations 


GENERAL  LAWS.  7 

is  the  fact  that  cyanide  of  sodium  is  formed  with  much  more  diffi- 
culty than  cyanide  of  potassium,  a  phenomenon  which  is  easily 
explained,  since  carbonate  of  sodium  is  less  easily  reducible  than 
carbonate  of  potassium. 

The  same  would  be  the  result  if  caustic  alkalis  were  used  instead 
of  carbonates.  That  cyanogen  and  oxygen  can  not  coexist  in  the 
same  medium  is  a  known  fact;  on  this  account  it  is  necessary  first 
to  reduce  the  oxygen  compounds  in  order  to  permit  the  formation 
of  cyanides. 

A  third  remark,  no  less  important,  to  add  to  the  two  preceding 
ones,  is  the  following:  If  a  current  of  nitrogen  be  passed  over  car- 
bon, heated  to  redness,  and  the  product  of  this  operation  be  brought 
into  contact  with  melted  potassium,  there  will  be  no  formation  of 
cyanide.  Against  these  convincing  facts  the  following  objection 
is  brought:  if  a  current  of  nitrogen  be  passed  over  a  mixture  of 
charcoal  and  baryta,  heated  to  a  temperature  lower  than  that 
necessary  for  the  reduction  of  the  base,  there  will  be  formed  a  cyanide 
of  barium  without  there  having  been  a  previous  formation  of  metallic 
barium. 

The  role  played  by  the  metal  would  therefore  seem  to  be  destroyed, 
and  the  statement  just  made  leads  immediately  to  the  discussion 
of  the  two  other  hypotheses:  formation  of  a  nitride  or  of  a 
carbide. 

Although  experiments  have  not  yet  clearly  proven  that  the 
formation  of  cyanides  is  possible  by  means  of  the  intermediate 
passage  through  a  nitride,  yet  this  method  of  formation  is  ex- 
plicable. Moissan,  who  prepared  nitride  of  calcium,  was  enabled, 
however,  by  bringing  this  body  in  contact  with  charcoal,  to  obtain 
only  very  small  quantities  of  cyanide. 

Finally,  it  is  a  fact  well  known  that  by  the  action  of  nitrogen 
on  the  carbides  of  the  alkaline  earths,  these  become  transformed 
into  cyanides.  This  phenomenon  may  explain  the  formation  of 
barium  cyanide  mentioned  above. 

It  is  not  at  all  improbable  that  the  same  reaction  takes  place 
with  the  carbides  of  the  alkali  metals,  although  thus  far  no  real 
experimental  data  prove  it.  It  still  remains  to  mention  Berthelot's 
hypothesis,  a  theory  quite  closely  related  to  that  of  the  carbides. 
This  investigator,  having  observed  that  nitrogen  and  acetylene  unite 


8  THE  CHEMISTRY  OF  CYANOGEN. 

directly  under  the  influence  of  the  electric  spark,  exploding  in  a 
mixture  of  these  gases  diluted  with  hydrogen: 

C2H2  +  N2  =  2CNH, 

supposes  that  the  formation  of  cyanides  is  preceded  by  that  of  the 
acetylide,  C2K2,  which,  like  acetylene,  would  unite  with  nitrogen. 

This  question  is  far  from  being  solved.  It  is  only  by  means 
of  thermochemical  studies  of  the  various  phenomena  which  con- 
trol these  combinations  that  a  clear  and  exact  idea  of  the  conditions 
under  which  they  are  formed  will  be  attained.  It  is  to  be  hoped 
that  modern  investigators  may  solve  this  problem;  this  would  be 
the  cause  of  great  progress  for  the  manufacture  of  cyanide  com- 
pounds. The  theory  of  the  formation  of  ferrocyanide  is  no  better 
known.  In  its  preparation,  by  means  of  nitrogenous  substances 
in  the  presence  of  potassium  carbonate,  a  cyanide  would  be  formed 
according  to  one  of  the  reactions  mentioned  above,  i.e.,  there  would 
be  formation  of  cyanogen,  reduction  of  the  carbonate  to  a  metallic 
state,  and  reaction  of  .the  cyanogen  on  the  metal  to  form  cyanide  of 
potassium.  The  role  which  iron  plays  is  unknown;  all  that  is  known 
is  that  the  ferrocyanide  is  formed  only  during  lixiviation,  yet  it  is 
necessary  that  iron  be  present.  The  reaction  takes  place  according 
to  the  following  equations : 

2CNK  +  Fe  =  (CN)  2Fe + K2, 
4CNK  +  (CN)  2Fe  =  Fe(CN)  6K4, 
or 

2CNK + FeS  =  (CN)  2Fe  +  K2S, 
4CNK  +  (CN)  2Fe  =  Fe(CN)6K4. 

The  presence  of  sulphide  of  iron  is  explained  as  follows :  Commer- 
cial potassium  carbonate  always  contains  a  certain  amount  of  sul- 
phate. This  sulphate  being  subjected  to  the  action  of  charcoal  and 
iron,  at  a  high  temperature,  generates  sulphide  of  iron  according  to 
the  following  equation : 

K2S04+4C=K2S+4CO, 

K2S+Fe+2C+2N-= 


GENERAL  LAWS  9 

In  his  treatise  on  "  Medicaments  chimiques,"  Prunier  puts  forth 
another  theory.  According  to  him,  nitride  of  carbon,  which  is 
produced  by  calcining  animal  substances,  would  react  on  potas- 
sium carbonate  in  order  to  form  acetylene.  This  gas  would  unite 
with  the  potassium  set  free  and  with  the  nitrogen  of  the  nitro- 
genous substance,  or  with  nitrogen  of  the  atmosphere,  according  to 
the  following  equation: 

C2H2 + K2  +  N2  =  2CNK  +  H2, 

when  the  iron  would,  in  its  turn,  react  to  form  cyanide  of  iron, 
which,  according  to  the  reaction  above  cited,  would  become  trans- 
formed into  ferrocyanide.  It  is  definitely  known  that  the  ferro- 
cyanide  is  not  formed  during  the  calcination,  for  at  that  tempera- 
ture the  ferrocyanide  would  be  decomposed,  giving  off  nitrogen 
and  forming  bicarbide  of  iron  and  potassium  cyanide,  according 
to  Liebig's  theory: 

Fe(CN)  6K4  =  N2  +  4CNK + C2Fe. 

The  formation  of  sulphocyanides,  which  is  readily  produced,  is 
easily  understood  because  cyanogen  remains  an  unsaturated  body, 
as  the  following  formula  shows : 

-C-N-, 

the  sulphur,  which  is  bivalent,  saturating  two  of  the  free  atoms, 
while  the  alkali  metal  saturates  the  last.  A  like  reasoning  may 
explain  the  formation  of  cyanates,  the  bivalent  oxygen  of  the  cya- 
nates  replacing  the  sulphur  of  the  sulphocyanides. 

To  sum  up  the  study  of  the  union  of  carbon  with  nitrogen  is 
interesting  from  more  than  one  point  of  view,  because  of  the  very 
difficulty  which  controls  its  formation  and  from  the  numerous  bodies; 
to  which  it  may  give  rise,  bodies  of  which  a  general  study  will  now 
be  made. 


CHAPTER  II. 

CHEMICAL  AND   PHYSICAL   STUDY   OF   CYANOGEN   AND  ITS 

DERIVATIVES. 

CYANOGEN,  C2N2  =  52. 

^MSifiS? 

100.00 

THE  formula  of  cyanogen  is  N=C-C=N.  It  is  really  a  nitride 
of  carbon.  <y^  £  H  N  —  til=  C, ,  <JL  oftA^fc  *$  "ruJCtf&i^ 

It  was  discovered  in  1814  by  Gay-Lussac,  who  gave  it  this  name 
because  it  formed  part  of  the  composition  of  Prussian  blue  (xv avocr) 
blue,  (fevvaw)  to  generate. 

This  discovery  exerted  considerable  influence  on  the  progress 
of  chemistry,  and  on  the  theories  at  that  time  admitted.  The 
investigations  of  Gay-Lussac  upon  this  body  which  he  had  jusi 
discovered  set  forth,  in  fact,  that  this  compound,  because  of  its 
properties,  resembles  greatly  the  halogens,  and  that  in  many  reac- 
tions it  behaves  like  a  simple  substance,  i.e.,  it  plays  the  role  of  an 
element.  In  fact  cyanogen  is  oftentimes  represented  by  the  simple 
formula  Cy,  instead  of  CN. 

Cyanogen  is  a  colorless  gas,  with  an  odor  reminding  one  of  bitter 
almonds.  It  exerts  a  decidedly  irritating  action  on  the  mucous 
membrane,  and  may  in  some  cases  even  cause  the  eyes  to  water. 

It  has  a  density  of  1.8064,  when  compared  with  air,  or  25.533 
(H  =  l).  One  liter  weighs  2.235  grams. 

One  volume  of  water  at  20°  C.  dissolves  4J  times  its  volume  of  gas, 
whereas  alcohol  dissolves  25  times  its  volume. 

It  becomes  a  liquid  at  20.7°  C.  under  ordinary  pressure,  and  at 

?  10 


CHEMICAL   AND   PHYSICAL  STUDY.  11 

15°  C.  under  a  pressure  of  4  to  5  atmospheres.     This  liquid  is  trans- 
parent and  mobile,  with  a  density  of  0.866. 

The  evaporation  of  this  liquid  in  open  air  causes  such  a  lower- 
ing of  temperature  that  the  portion  not  evaporated  becomes  solid. 
Solid  cyanogen  melts  at  -34°  C. 

Cyanogen  gas  burns  in  air  with  a  purple  flame,  producing  nitro- 
gen and  carbonic  acid: 

=  C02+N. 


It  is  readily  decomposed  by  heat.  Its  formation  is  endothermic, 
and  that  is  the  reason  why  it  cannot  be  obtained  by  the  direct  union 
of  carbon  and  nitrogen.7—  <^//3- 

The  electric  spark  breaks  it  up  into  its  elements;  a  mixture  of 
1  vol.  of  cyanogen  and  2  vols.  of  oxygen  explodes  under  the  influ- 
ence of  the  electric  spark  into  1  vol.  of  nitrogen  and  2  vols.  of  car- 
bonic acid. 

An  aqueous  solution  of  cyanogen  becomes  quickly  altered  in  the 
light;  a  black  flocculent  precipitate,  called  azulmic  acid,  Cyn(H20)n 
or  C4H4N402,  separates  out,  caused  by  the  union  of  4  equivalents 
of  water  and  4  equivalents  of  cyanogen,  while  in  the  solution  there 
remain  carbonic  anhydride,  hydrocyanic  acid,  ammonia,  urea,  and 
ammonium  oxalate  (Woehler). 

The  same  result  is  observed  in  an  alcoholic  or  ether  solution. 
The  presence  of  an  acid  suffices  to  prevent  these  transformations. 
The  same  substances  are  produced  in  an  ammoniacal  solution  as  in 
an  aqueous  solution. 

Cyanogen  does  not  unite  directly  with  hydrogen.  If  a  mix- 
ture of  equal  volumes  of  cyanogen  and  hydrogen  be  passed  in  a 
tube  heated  to  500°  C.,  only  traces  of  hydrocyanic  acid  are  obtained. 

On  the  other  hand,  cyanogen  unites  with  nascent  hydrogen,  pro- 
ducing ethylene  diamine;  finally,  if  sealed  tubes  heated  to  500°  C. 
are  employed,  the  union  of  the  two  gases  is  complete. 

Cyanogen  does  not  unite  directly  with  chlorine,  even  in  the 
light;  but  if  the  two  gases  are  moist,  an  oily  liquid  and  a  solid 
aromatic  substance  are  formed. 

On  the  other  hand,  cyanogen  is  decomposed  by  hypochlorous 
anhydride,  and  by  hypochlorous  acid,  with  formation  of  carbonic 
acid,  chlorine,  nitrogen,  and  gaseous  cyanogen  chloride. 


12  THE  CHEMISTRY  OF  CYANOGEN. 

It  does  not  unite  directly  with  sulphur,  but  when  cyanogen  and 
hydrogen  sulphide  are  brought  together  in  a  moist  state  two  crys- 
tallizable  compounds  are  formed,  a  monosulphydrate  and  a  bisul- 
phydrate  of  cyanogen,  corresponding  respectively  to  the  formulas 
C2N2.SH2  and  C2N2.(H2S)2.  The  mono-  or  the  bisulphydrate  is 
obtained  according  as  an  excess  of  cyanogen  or  of  hydrogen  sul- 
phide is  used. 

In  a  heated  state,  cyanogen  absorbs  potassium,  with  formation 
of  potassium  cyanide.  An  aqueous  solution  of  potash  absorbs  the 
gas  energetically,  with  formation  of  azulmate  of  cyanide,  cyanate 
and  oxalate  of  potassium. 

It  combines  directly  with  zinc,  with  cadmium  at  300°  C.,  and 
with  lead  at  500°  C.  Heated  to  redness  with  iron,  the  latter  absorbs 
the  carbon,  setting  the  nitrogen  free,  the  metal  becoming  brittle. 
With  the  other  metals  it  unites  only  indirectly. 

Some  organic  bases  may  unite  with  it,  e.g.,  aniline,  toluidine, 
codeine,  producing  cyaniline,  cyanotoluidine,  cyanocodeine,  respect- 
ively, bodies  which  may  be  decomposed  by  an  alkali  with  formation 
of  oxalic  acid  or  its  derivatives.  Cuprous  chloride  absorbs  it.  It  is 
decomposed  by  manganic  sulphate,  which  reduces  it  to  carbonic 
acid  and  nitrogen.  Mercurous  oxide  absorbs  it  slowly. 

Potassium  carbonate,  heated  to  redness,  absorbs  cyanogen,  with 
production  of  cyanide  and  cyanate  of  potassium. 

Properly  stated,  cyanogen  does  not  exist  free.  Yet,  in  certain 
cases  it  is  found  in  small  quantities,  as,  for  example,  in  the  gases 
of  the  blast-furnace,  where  one  finds  as  much  as  1.34%.  It  is  also 
formed  when  a  mixture  of  illuminating-gas  and  ammonia  is  burned 
in  a  Bunsen  burner. 

It  is  formed,   indirectly,   in  the  following  reactions: 

(1)  When  nitrogenous  animal  substances  are  burned  in  pres- 
ence of   an   alkali   carbonate,   particularly   potassium  carbonate. 

(2)  When  nitrogenous  animal  substances  are  burned  in  the  pres- 
ence of  potassium. 

(3)  When  nitrogen  acts  on  a  mixture  of  charcoal  and  potash. 

(4)  When  ammonia  acts  on  charcoal,  heated  to  redness. 

In  these  reactions,  however,  it  is  always  combined;  and  it  is 
as  a  cyanide  of  potassium,  sodium,  or  ammonium  that  it  may  be 
extracted.  These  methods  of  formation  constitute  the  base  of  the 


CHEMICAL   AND   PHYSICAL  STUDY.  13 

process  of  the  manufacture  of  alkali  cyanides,  of  which  more  in  a 
later  chapter. 

Cyanogen  may  be  prepared  by  various  methods. 

(1)  By  heating  dry  mercuric  cyanide  to  dull  redness  in  a  retort: 

Hg(CN)  2  =  (CN)  2  +  Hg  (Gay-Lussac) . 

(2)  By  heating  in  a  retort  an  intimate  mixture  of  2  parts  potas- 
sium ferrocyanide  and  3  parts  of  mercuric  chloride  (Kemp). 

(3)  By  the  dry  distillation  of  ammonium  oxalate  or  of  oxamide: 

C204(NH4)  2  =  4H20  +  (CN)  2. 

(4)  By   heating   glycerine   and   ammonium   oxalate   at   200°  C. 
(Storch). 

(5)  By  heating,  on  an  oil-bath  at  160-170°  C.,  a  dry  mixture 
of  zinc  cyanide  and  cupric  chloride,  there  is  formed  cupric  cyanide 
which,  under  the  influence  of  heat,  loses  one  half  of  its  cyanogen, 
and  becomes  transformed  into  cuprous  cyanide  and  cyanogen. 

It  is  likewise  produced  by  heating,  under  the  same  conditions, 
a  solution  of  copper  sulphate  into  which  a  concentrated  solution 
of  potassium  cyanide  is  gradually  poured  (Varet) 

Finally,  cyanogen  is  formed  with  an  absorption  of  heat — 38 
calories,  when  carbon  in  the  state  of  the  diamond  is  used: 

C(diamond)  +  N  =  CN  -  38  cal. 
PARACYANOGEN  (CN)». 

This  is  a  polymeric  modification  or  an  isomer  of  cyanogen,  which 
is  always  produced  in  the  preparation  of  cyanogen  by  the  decom- 
position of  the  cyanides  of  mercury  or  of  silver  by  heat,  the  amount 
of  paracyanogen  increasing  in  proportion  as  the  temperature  is  low. 

It  is  also  obtained  by  heating  cyanogen  in  a  closed  vessel;  but, 
on  the  other  hand,  when  paracyanogen  is  likewise  heated  out  of 
contact  with  air  it  is  decomposed  into  cyanogen.  However,  when 
the  vapor  of  cyanogen  exerts  a  definite  pressure  on  the  paracyanogen 
remaining,  the  production  of  the  former  ceases.  This  tension  of 
transformation  varies  proportionally  with  the  temperature,  but  it 
is  constant  for  a  given  temperature. 


14 


THE  CHEMISTRY  OF  CYANOGEN 


Troost  and  Hautefeuille  determined  the  conversion  tension  of 
cyanogen: 


Temperature. 

Tension  of 
Transformation. 

Temperature. 

Tension  of 
Transformation. 

502 

54  mm. 

599 

275  mm. 

559 

125     " 

601 

318     " 

575 

129     " 

620 

868    " 

587 

157     " 

640 

1310     " 

This  is  therefore  a  phenomenon  quite  analogous  to  that  of  the 
allotropic  transformation  of  white  phosphorus  into  red  phosphorus. 

Paracyanogen  is  a  brownish-black  powder,  insoluble  in  water, 
soluble  in  concentrated  sulphuric  acid.  It  becomes  converted  into 
cyanogen  on  heating  in  a  current  of  inert  gas,  such  as  carbonic 
acid  or  nitrogen. 

HYDROCYANIC  ACID  (PRUSSIC  ACID),  CNH=27. 

f  C  =  44.44 

100CNH=  |N  =  51.85 
lH=  3.71 

100.00 

Hydrocyanic  acid  or  nitride  of  formic  acid  has  the  formula 
CNH.  It  is  also  called  prussic  acid.  It  was  discovered  by  Scheele 
in  1782,  but  Gay-Lussac  was  the  first  to  obtain  it  in  a  pure  state, 
in  1811,  and  to  establish  its  composition.  It  was  known  to  Egyptian 
priests,  who  used  it  in  the  killing  of  traitors. 

It  occurs  in  certain  plants;  in  the  leaves  of  the  laurel-cherry 
and  the  laurel-leaf  willow,  in  the  leaves  and  blossoms  of  the  peach, 
and  in  bitter  almonds.  The  kernels  of  most  of  the  stone-fruits 
contain  some.  The  root  of  Jatropha  Mannihot  also  contains  it, 
from  which  it  may  be  obtained  by  distillation  with  water. 

It  is  produced  by  the  breaking  up  of  the  amygdalin,  a  neutral 
substance  found  in  various  plants,  by  the  action  of  water. 

It  is  the  hydrocyanic  acid  which  gives  to  liquors  prepared  with 
almonds  their  characteristic  odor  and  flavor. 

Hydrocyanic  acid  is  sometimes  obtained  in  the  distillation  of 
nitrogenous  products,  and  in  the  oxidation  of  certain  organic  sub- 
stances with  nitric  acid. 


CHEMICAL  AND   PHYSICAL  STUDY.  15 

Formate  of  ammonium  heated  to  200°  C.  loses  water  and  forms 
hydrocyanic  acid: 

CH02.NH4-2H20  = 


The  action  of  the  electric  spark  on  a  mixture  of  acetylene  and  nitro- 
gen gives  hydrogen  cyanide: 

C2H2+N2=2CNH  (Berthelot). 

When  an  electric  furnace  is  started,  a  perceptible  odor  of  laurel- 
cherry,  due  to  hydrocyanic  acid,  is  noticed.  This  is  produced  by 
the  union  of  atmospheric  nitrogen  with  acetylene,  which  latter  is 
formed  by  the  union  of  the  carbon  of  the  electrodes  with  the  hydrogen 
due  to  the  decomposition  of  water-  vapor  by  the  voltaic  arc.  Hydro- 
gen cyanide  is  also  produced  by  the  action  "of  chloroform  on 
ammonia  : 

=  3HC1+CNH. 


It  is  likewise  produc  d  in  appreciable  quantities  in  the  combustion 
of  a  mixture  of  air  and  nitrogen  dioxide  in  an  inverted  Bunsen 
burner;  likewise  in  tobacco-smoke;  and  by  the  passage  of  an  electric 
discharge  in  9%  aniline;  and  in  the  electric  arc 

To  obtain  it  pure,  mercuric  cyanide  is,  as  a  rule,  decomposed  by 
hydrochloric  acid  (Gay-Lussac)  when  there  is  formed  hydrocyanic 
acid  and  corrosive  sublimate;  but,  on  account  of  the  affinity  of  this 
salt  for  hydrocyanic  acid,  the  yield  is  rather  small  This  can  be 
remedied  by  the  addition  of  ammonium  chloride,  which  unites  with 
the  sublimate  (Bussy  &  Buignet): 

(CH)  2Hg  +  2HC1  =  HgCl2  +  2CNH. 

The  best  procedure  consists  in  treating  potassium  ferrocyanide 
with  sulphuric  acid  (15  parts  ferrocyanide,  7  sulphuric  acid,  9  water;. 
The  gas  first  passes  over  calcium  chloride,  and  is  then  collected  in  a 
cylinder  surrounded  by  a  cooling  mixture.  In  this  way  the  anhy- 
drous acid  is  obtained.  To  obtain  the  aqueous  acid,  it  is  only  neces- 
sary to  distil  the  mixture: 

2[Fe  (ON)  6K4]  +  3H2S04  -  3K2SO4  +  6CNH  +  Fe(CN)  6K2Fe. 
Several  other  processes  have  been  brought  out: 


16  THE  CHEMISTRY  OF  CYANOGEN. 

Clarke's  process,  which  consists  in  adding  4  parts  of  potassium 
cyanide  to  a  solution  of  9  parts  of  tartaric  acid  in  60  parts  of  water. 
In  this  case  cream  of  tartar  separates  out,  leaving  a  supernatant 
liquid  of  hydrocyanic  acid. 

Everitt's  process  is  based  on  the  decomposition  of  silver  cyanide 
by  hydrochloric  acid: 

CNAg  +  HC1  -  CNH  +  AgCl. 

Thompson's  process  is  based  on  the  decomposition  of  lead 
cyanide  by  sulphuric  acid: 

(CN)  2Pb  +  H2S04  =  2CNH  +  PbS04. 

Vauquelin's  process  consists  in  passing  a  current  of  hydrogen 
sulphide  over  very  dry  mercuric  cyanide. 

Kuhlmann's  process  is  likewise  of  interest.  Dry  ammonia  gas  is 
passed  through  a  glass  tube  filled  with  pieces  of  charcoal,  and  heated 
to  redness.  The  gas  formed  is  conducted  through  dilute  sulphuric 
acid  at  50°  C.,  and  then  into  a  cooled  receiver.  Ammonium  cyanide 
is  formed,  which  in  contact  with  sulphuric  acid  forms  ammonium 
sulphate  and  hydrocyanic  acid: 


=  CN-NH4+H2 

2(CN  •  NH4)  +H2S04  --  2CNH  +  (NH4)2S04. 

The  anhydrous  acid  is  a  colorless  liquid  of  specific  gravity  0.7058 
at  7°C.,  and  0.6969  at  18°  C.  It  becomes  a  solid  at  -15°C.,  boils 
at  26.5°  C.  Its  vapor  density  is  0.9467. 

Its  odor  is  characteristic  of  bitter  almonds.  It  is  soluble,  or 
rather  miscible  with  water  and  alcohol  in  all  proportions.  The 
density  of  its  aqueous  solutions  decreases  in  proportion  as  the 
amount  of  acid  in  solution  increases.  Thus  a  1%  solution  has  a 
specific  gravity  of  0.9988,  while  a  16%  solution  has  a  specific  gravity 
of  only  0.9570.  Its  aqueous  solution  is  a  union.  In  fact,  if  equal 
parts  of  the  two  bodies  be  mixed,  a  loss  of  25%  in  vapor-tension  is 
produced.  When  dry,  it  burns  in  air  with  a  white  flame  tinged  with 
violet,  with  formation  of  water,  carbonic  acid,  and  nitrogen: 

2CNH  +50  =H20  +2C02  +N2. 


CHEMICAL  AND  PHYSICAL  STUDY.  17 

It  decomposes  rapidly  in  the  light,  yielding  ammonia  and  a  brown 
deposit. 

The  presence  of  a  small  quantity  of  mineral  acid  renders  it  more 
stable.  A  trace  of  ammonia  decomposes  it  very  rapidly.  Concen- 
trated mineral  acids  transform  it  very  quickly  by  fixing  2  molecules 
of  water  into  formic  acid  and  ammonia.  Dilute  alkalis,  in  the  cold, 
produce,  with  it,  the  corresponding  cyanides: 

KOH + CNH  =  CNK  =  H20 ; 

but  when  boiled,  or  with  concentrated  alkalis,  there  is  a  formation 
of  alkali  formate  and  ammonia: 

CNH  +  KOH  +  H20  =  NH3  +  HCOOK 

It  is  likewise  decomposed  by  chlorine  and  bromine,  yielding 
hydrochloric  acid,  hydrobromic  acid,  and  crystalline  compounds, 
such  as  hydrochloride  and  hydrobromide  of  cyanogen. 

In  the  presence  of  slightly  warmed  potassium  it  yields  potassium 
cyanide. 

Nascent  hydrogen  reduces  it  to  methylamine: 

CNH  +  H4  =  CH3NH2  (Mendius). 

Heat  breaks  it  up  into  hydrogen,  cyanogen,  nitrogen,  and  carbon. 
The  electric  spark  decomposes  it  nearly  completely  only  when  it 
is  mixed  with  hydrogen,  or  when  it  is  in  an  aqueous  solution. 

Manganese  dioxide  absorbs  gaseo  s  hydrocyanic  acid  entirely 
when  mixed  with  hydrogen.  It  is  a  weak  acid  which  does  not  de- 
compose carbonates.  It  is  formed  by  the  union  of  equal  volumes 
of  hydrogen  and  cyanogen  without  condensation. 

Action  on  the  System. — Prussic  acid  is  the  most  violent  and  rapid 
poison  known.  A  dose  of  5  centigrams  suffices  to  kill  a  man.  One 
drop  of  this  acid  placed  on  the  tongue  of  a  dog  renders  him  instantly 
unconscious.  Scheele,  the  discoverer  of  hydrocyanic  acid,  himself 
died,  poisoned  by  it.  Scharinger,  a  chemist  of  Vienna,  died  in  two 
hours,  the  result  of  letting  two  drops  of  this  acid  fall  on  his  arm. 

Its  vapors  are  likewise  extremely  poisonous.  Their  respiration 
causes  violent  headaches,  nausea,  pains,  and  oppression  in  the  chest. 

In  gold-mines  where    the  cyanide   process  is  in  use,  workmen 


18  THE  CHEMISTRY  OF  CYANOGEN. 

whose  duty  it  is  to  clean  the  vats  are  affected  with  general  weak- 
ness, headaches,  dizziness,  and  nausea.  Often  a  kind  of  eruption, 
especially  on  the  arms,  breaks  out  in  them.  These  eruptions  may 
be  readily  overcome  by  internal  and  external  application  of  potassium 
ferrocyanide. 

Prussic  acid  seems  to  affect  the  circulatory  rather  than  the  nervous 
system;  it  destroys  muscular  sensibility,  and  death  results  through 
suspension  of  the  heart's  action. 

Quite  often  the  victim  is  seized,  before  death,  by  violent  attacks 
of  tetanus. 

Properly  speaking,  there  is  no  antidote  for  prussic  acid.  Inhala- 
tion of  chlorine  and  of  ammonia  have  been  advised,  but  ammonium 
cyanide  and  cyanogen  chloride  are  themselves  just  as  poisonous. 

If  these  bodies  have  sometimes  produced  favorable  effects,  these 
must  rather  be  attributed  to  an  excitation  of  the  nervous  system. 
Likewise,  internal  application  of  essence  of  turpentine  (30  grams 
in  emulsion  by  spoonful)  have  been  advised.  The  affusion  of 
cold  water  on  the  spinal  column  and  on  the  base  of  the  skull  are 
recommended. 

Robert  and  Krohl  have  quite  recently  p  aised  the  use  of  hydrogen 
peroxide  as  an  antidote  for  prussic  acid  A  30%  solution  is  used 
internally,  and  a  3%  solution  for  subcutaneous  injections.  The 
following  reaction  takes  place:  the  hydrocyanic  acid,  reacting  with 
hydrogen  peroxide,  is  changed  into  oxamide,  which  is  non-poisonous  : 


This  method  has  been  quite  successfully  used  in  the  English  gold- 
mines for  the  past  four  years,  and  in  many  cases  subcutaneous 
injection  suffices.  Dr.  Autal  of  the  Austria-Hungary  Medical 
Association  (June  2,  1894)  recommended  the  use  of  cobalt  nitrate. 
This  salt  forms  with  potassium  cyanide  an  insoluble  and  harmless 
compound. 

METALLIC  CYANIDES. 

By  its  union  with  metals,  hydrocyanic  acid  forms  cyanides  or 
cyanhydrates,  salts  which  are  analogous  to  chlorides,  bromides,  and 
iodides. 


CHEMICAL  AND  PHYSICAL  STUDY.  19 

Cyanides  may  be  divided  into  two  classes,  simple  and  double 
cyanides. 

The  simple  cyanides,  especially  the  alkali  cyanides,  are  formed 
in  many  reactions : 

(1)  By  the  action  of  cyanogen  or  of  gaseous  hydrocyanic  acid 
on  the  slightly  heated  metal. 

(2)  By  heating  carbonates  or  hydrates  of  alkalis  in  a  current 
of  cyanogen. 

(3)  By  double  decomposition  of  hydrocyanic  acid  and  metallic 
hydrates. 

(4)  By  the  action  of  a  current  of  nitrogen  upon  a  mixture  of 
charcoal  and  hydrate  or  carbonate  of  an  alkali. 

(5)  By  the  ignition  of  nitrogenous  organic  substances  in  the 
presence  of  alkalis,  hydrates  or  carbonates,  nitrites  or  nitrates. 

(6)  By  the    action  of   ammonia-gas    upon  charcoal,   heated  to 
redness,  or  of  carbon  monoxide  upon  ammonia,  likewise  at  a  red 
heat: 

2NH3-fC  =  CN-NH4+2H. 

As  to  the  other  cyanides,  they  are  generally  obtained  by  the 
double  decomposition  between  a  metallic  salt  and  an  alkali  cyanide. 

Properties.— The  cyanides  of  the  alkali  metals  and  of  the  alkaline 
earth  metals  are  soluble  in  water  and  in  alcohol,  with  formation 
of  a  strong  alkaline  solution;  the  cyanides  of  the  other  metals  are 
insoluble,  excepting  mercuric  cyanide.  The  cyanides  of  the 
alkalis  and  of  the  alkaline  earths  are  not  decomposed  by  heat,  in 
the  absence  of  air;  but  in  contact  with  oxygen  they  are  transformed 
into  cyanates: 

CNK  +  0=CNOK. 

The  other  cyanides  are  decomposed  by  heat.  In  the  presence  of 
water  and  of  heat  they  are  all  decomposed.  Cyanides  of  the  heavy 
metals  give  carbon  monoxide,  carbon  dioxide,  ammonia,  carbon, 
and  the  metal;  the  other  cyanides  give  formates  and  ammonia. 

Cyanides  have  reducing  properties.  They  reduce  metallic  oxides, 
being  themselves  transformed  into  cyanates. 

Mineral   acids,   e.g.,   hydrochloric,    sulphuric,   decompose   them, 


20  THE  CHEMISTRY  OF  CYANOGEN. 

setting  free  hydrocyanic  acid.     Nitric  acid  decomposes  them  into 
nitrates,  carbonic  acid,  and  nitrogen: 

CNK  +  2HN03  =  KN03  +  C02 + 2N  +  H20. 

When  the  oxides  of  the  heavy  metals  are  digested  with  a  solu- 
tion of  an  alkali  cyanide,  a  large  part  of  them  is  converted  into 
cyanides,  whereas  the  alkali  metal  becomes  hydrated: 

2CNK + HgO  +  H20  =  Hg(CN)  2  +  2KOH. 

They  unite  with  the  metallic  chlorides,  bromides,  iodides,  nitrates, 
and  chromates. 

POTASSIUM  CYANIDE,  CNK  =  65. 

=  18.46 

100CNK=  -I  N  =  21.54 
=  60.00 


100.00 

Potassium  cyanide,  KCN  =  65,  is  a  white  substance  having  an 
acrid  and  slightly  bitter  taste,  leaving  an  after-taste  of  hydro- 
cyanic acid.  It  has  a  strong,  penetrating  odor  which  is  character- 
istic. It  crystallizes  in  anhydrous  octohedrons,  which  are  easily 
fusible  and  deliquescent.  It  has  an  alkaline  reaction.  It  is  vola- 
tile at  a  white-red  heat  without  decomposition.  It  is  easily  soluble 
in  cold,  more  so  in  boiling  water  (100  parts  boiling  water  dissolve 
122  parts),  slightly  soluble  in  strong  alcohol.  Its  solubility  in  alco- 
hol increases  in  proportion  as  the  alcohol  is  diluted. 

When  in  solution,  or  even  in  a  moist  state,  it  is  acted  upon  by 
carbonic  acid,  with  formations  of  hydrocyanic  acid  and  potas- 
sium carbonate: 

2CNK + C02  +  H20  =  K2C03  +  2CNH. 

-  This  reaction  is  of  great  importance  from  the  manufacturing 
standpoint;  for  it  shows  how  little  stable  that  body  is,  and  the. 
means  necessary  to  be  taken  to  prevent  its  decomposition  and  to 
keep  it  intact. 

When  its  aqueous  solution  is  heated  to  boiling  out  of  contact 
with  air,  it  breaks  up  into  potassium  formate  and  ammonia.  In 
this  way  it  may  be  completely  decomposed. 


CHEMICAL  AND  PHYSICAL  STUDY.  21 

Dry  carbonic  acid  like  dry  air  does  not  react  on  dry  potassium 
cyanide.  It  is  easily  oxidized,  which  means  that  it  is  an  energetic 
reducing  agent.  When  burned  in  air,  or  with  manganese  dioxide, 
or  with  iron  oxide,  it  is  converted  into  a  cyanate.  This  property 
was  the  cause  of  its  being  used  in  the  reduction  and  separation  of 
certain  metallic  oxides;  it  has  the  advantage  over  other  reducing 
agents  of  not  carburetting  the  metal.  This  reaction  takes  place 
generally  at  temperatures  only  slightly  raised.  It  is  likewise 
oxidized  by  chloride  of  lime,  which  converts  it  into  cyanate  of  lime. 
When  its  aqueous  solution  is  treated  by  an  electric  current  it  is 
converted  into  cyanate. 

It  also  works  as  a  reducing  agent  in  a  wet  way. 

When  fused  with  sulphur  it  is  changed  into  sulphocyanide: 

• 

CNK  +  S  =  CNKS. 

This  same  result  is  obtained  when  it  is  fused  with  sulphide  of 
tin  or  of  antimony. 

Its  aqueous  solution  dissolves  several  metallic  oxides,  and  even 
metals;  e.g.,  copper,  zinc,  nickel,  iron.  Mercury,  platinum,  tin 
are  not  dissolved  by  it;  cadmium,  silver,  gold  are  dissolved  by 
it,  but  only  in  contact  with  air.  This  last  property  is  of  the 
greatest  importance,  for  to  it  is  due  the  development  of  the 
manufacture  of  the  alkali  cyanides.  Likewise,  chloride  of  silver, 
selenium,  tellurium,  and  iodine  are  dissolved  by  it.  In  the  case 
of  iodine  there  is  formed  cyanogen  iodide,  or  a  double  iodide  of 
cyanogen  and  potassium. 

Heated  with  nitrate  or  chlorate  of  potassium  a  violent  explosion 
takes  place.  When  potassium  sulphate  is  fused  with  potassium 
cyanide,  the  latter  becomes  converted  into  cyanate  of  potassium, 
and  there  is  also  formed  potassium  sulphide.  When  hydrogen 
sulphide  is  passed  through  a  concentrated  aqueous  solution  of  potas- 
sium cyanide,  an  intense  red  coloration  results,  with  formation  of 
yellow  needles  of  chryseane,.  CJIsH^. 

When  sulphurous  acid  is  passed  through  a  cooled  40%  solution 
of  potassium  cyanide  hydrocyanic  acid  is  set  free,  the  solution 
becomes  brown,  and  in  a  few  days  there  are  formed  crystals  of  cyano- 
sulphite  of  potassium,  S02CNK  +  H20,  a  solution  which  possesses 


22  THE  CHEMISTRY  OF  CYANOGEN. 

the  property  of  reducing  salts  of  gold  and  silver.  When  this  solu- 
tion is  treated  with  acids  there  is  formed  acid  -  cyanosulphite  of 
potassium,  which  is  only  slightly  soluble  and  decomposable  by  heat. 

Potassium  cyanide  is  decomposed  by  permanganate  of  potash. 

The  most  remarkable  and  interesting  property  of  potassium 
cyanide  is  that  of  dissolving  gold  in  the  presence  of  the  oxygen 
and  moisture  of  the  atmosphere,  since  this  property  is  the  cause 
of  its  extensive  use  in  industry.  This  solution  takes  place  according 
to  the  following  reactions: 

4CNK  +  Au2  +  0  +  H20  =  2([CN]2KAu)  +  2KOH. 

When  treated  with  zinc,  this  new  compound  yields  metallic 
gold,  with  formation  of  a  double  cyanide  of  zinc  and  potassium: 


2([CN]2KAu)  +  Zn  =  2(CNK,[CN]2Zn)  +Au2. 

In  reality  the  reaction  takes  place  in  another  way;  at  least 
it  is  explained  in  the  following  manner:  Zinc  causes  the  formation 
of  a  voltaic  couple,  and  in  general,  where  the  solution  contains 
potassium-gold-cyanide  and  cyanide  of  potassium  in  excess,  and 
zinc,  the  following  reactions  fake  place: 

4CNK  +  Zn  +  2H20  =  2(CNK,[CN]2Zn)  +  2KOH  +  H2; 

2[(CN)  2KAu]  +  H2  =  2CNH  +  2CNK  +  Au2, 

CNH  +  KOH  =  CNK  +  H20. 

Not  its  least  interesting  property  is  that  of  dissolving  certain  metallic 
sulphides,  such  as  those  of  copper,  silver,  gold,  zinc,  iron,  which 
may  be  used  in  metallurgy. 

Finally,  it  possesses  extremely  toxic  properties.  Two  centi- 
grams of  this  salt  suffice  to  cause  the  death  of  a  man. 

In  case  of  poisoning  by  this  compound,  the  following  treatment 
is  recommended:  Cause  the  patient  to  breathe  chlorinated  water, 
liquor  of  Labarraque,  or  ammonia;  administer  doses  of  essence  of 
turpentine  (30  grams  in  emulsion)  or  multiple  antidote  of  Jeannel; 
affusions  of  cold  water  on  the  head,  anodynes,  and  tonics. 


CHEMICAL  AND  PHYSICAL  STUDY.  23 

CYANIDE  OF  SODIUM  CNNa  =  49. 

f  C   =24.49 

100CNNa  =  i  N   =28.57 
lNa  =  46.94 

100.00 
« 

It  corresponds  to  the  formula  CNNa  =  49. 

It  is  formed  in  the  same  way  as  is  potassium  cyanide.  Its'  prop- 
erties are  almost  identical.  It  is  rather  difficult  to  obtain  it  in 
crystalline  form,  for  its  aqueous  solution  evaporates  in  a  mass. 
The  only  important  difference  between  sodium  and  potassium 
cyanide  is  that  the  former  contains  more  cyanogen,  which  is  to 
its  advantage  For  example,  the  atomic  weight  of  CNNa  is  49, 
of  which  26  is  cyanogen,  i.e.,  53%,  while  the  atomic  weight  of  CNK 
is  65,  of  which  26  is  cyanogen,  or  only  40%. 

On  account  of  the  progress  of  electrochemistry  in  preparing 
metallic  sodium  in  large  quantities  and  at  a  moderate  price,  sodium 
cyanide  is  daily  becoming  of  greater  importance. 

Yet  the  use  of  potassium  cyanide  is  preferred  in  industry,  because 
it  is  not  deliquescent  and  therefore  may  be  more  easily  transported. 
At  present  a  double  cyanide  of  sodium  and  potassium  is  being  pre- 
pared (CN)2NaK,  which  makes  possible  the  use  of  a  larger  quantity 
of  free  cyanogen  under  a  less  weight. 

AMMONIUM  CYANIDE,  CN-NH4  =  44. 

r  C  =  27.27 
100CN-NH,=  |  N  =  63.63 

LH=  9.10 


100.00 

Ammonium  cyanide  or  cyanhydrate  of  ammonia,  CN-NH4  =  44, 
is  a  solid,  colorless  product  crystallizing  in  cubes  or  quadrangular 
prisms.  It  has  an  alkaline  reaction,  and  an  odor  reminding  one  of 
both  hydrocyanic  acid  and  ammonia.  It  is  readily  soluble  in  water 
and  alcohol,  and  quite  unstable  in  air,  especially  when  heated.  At 
36°  C.  it  undergoes  partial  volatilization  and  is  converted  into  azul- 
mic  acid.  Its  vapors  are  inflammable.  It  is  very  poisonous. 

It  may  be  prepared  as  follows: 

(1)  By  the    action  of  ammonia  on  charcoal  heated  to  redness 


"24  THE  CHEMISTRY  OF  CYANOGEN. 

if  the  product  of  the  reaction  be  collected  in  a  cylinder  surrounded 
.by  a  freezing  mixture: 

C+2NH3  =  CN-NH4+H2. 

(2)  By  the  double  decomposition  of  ammonium  chloride  and 
the  cyanides  of  potassium  or  of  mercury,  or  ferrocyanide  of  potas- 
sium. Ammonium  cyanide  exists  already  formed,  as  will  be  seen 
later,  in  illuminating-gas 

CALCIUM  CYANIDE,  Ca(CN)2  =  92. 

rC   =26.09 

100Ca(CN)2  =  \  N  =30.43 
LCa  =  43.48 


100.00 

It  occurs  as  anhydrous  crystalline  cubes,  soluble  in  water.  Its  solu- 
tion is  decomposed  by  heat  and  carbonic  acid.  It  is  prepared  by 
the  action  of  hydrocyanic  acid  on  a  solution  of  lime  or  on  milk  of 
lime. 

BARIUM  CYANIDE,  Ba(CN)2  =  189. 

rC   =12.70 

100Ba(CN)2=  \  N  =14.81 
Ba  =  72.49 

100.00 

It  is  obtained  by  heating  ferrocyanide  of  barium  in  a  closed 
tube  (Berzelius),  or  by  saturating  baryta  water  with  hydrocyanic 
acid  (Ittner),  or,  still  more  easily,  by  the  action  of  nitrogen  upon  a 
mixture  of  charcoal  and  of  baryta  heated  to  redness  (Margueritte 
and  Sourdeval).  This  last  reaction  has  been  applied  industrially. 

It  is  soluble  in  water  and  in  alcohol  and  is  decomposed  by  heat. 
For  a  long  time  its  use  has  been  praised  in  metallurgy  for  the  cemen- 
tation of  steel. 

ALUMINUM  CYANIDE. 

This  is  not  yet  known. 

CYANIDE  OF  ZINC,  Zn(CN)2  =  117. 

rC    =20.51 
100Zn(CN)2  =     N  =23.93 


100.00 


CHEMICAL  AND  PHYSICAL  STUDY.  25 

It  is  a  white  substance,  insoluble  in  water  and  in  alcohol,  soluble 
in  the  alkali  cyanides  with  formation  of  double  cyanides.  It  is 
prepared  either  by  the  double  decomposition  of  zinc  sulphate  and 
potassium  or  ammonium  cyanide,  or  by  the  action  of  hydrocyanic 
acid  on  the  acetate  or  hydrate  of  zinc. 

IRON  CYANIDES. 

The  simple  cyanides  of  iron  are  little  known,  because  of  the^ 
extreme  ease  with  which  they  are  transformed  into  the  complete- 
cyanides. 

Two  of  them  are  known  from  which  a  whole  series  of  double  salts,' 
are  derived:  they  are  ferrous  cyanide,  Fe(CN)2,  and  ferric  cyanide,. 
Fe2(CN)6.  The  ferrocyanides  correspond  to  the  former,  while  the? 
ferricyanides  are  derived  from  the  latter. 

CHROMIUM  CYANIDES. 

Chromous  cyanide,  Cr(CN)2,  is  white  It  is  obtained  by  pre- 
cipitating a  solution  of  chromous  chloride  with  potassium  cyanide. 
It  is  soluble  in  an  excess  of  potassium  cyanide  and  is  easily  changed 
in  the  air,  giving  oxide  of  chromium  and  chromic  cyanide. 
Chromic  cyanide,  Cr2(CN)6,  is  more  stable;  it  is  obtained  by  pre- 
cipitating at  the  boiling-point  a  solution  of  chromic  chloride  with 
an  excess  of  potassium  cyanide.  These  two  cyanides  form  respect- 
ively chromous  and  chromic  cyanides,  analogous  to  ferrous  and 
ferric  cyanides. 

CYANIDE  OF  MANGANESE. 

Only  the  double  cyanides  are  known,  Manganous  and  manganic 
cyanides,  which  will  be  studied  later. 

CYANIDE  OF  TIN. 
This  is  unknown  in  a  free  state. 

CYANIDE  OF  LEAD,  Pb(CN)2=258. 

fC    =  9.30 

100Pb(CN)3=  JN  =10.85 
LPb  =  79.85 

100.00 


26  THE  CHEMISTRY  OF  CYANOGEN. 

It  is  but  imperfectly  known.  When  prepared  by  the  action  of 
ammonium  cyanide  and  lead  acetate  it  is  yellow,  while,  when  it 
is  obtained  by  the  addition  of  hydrocyanic  acid  to  an  ammoniacal 
solution  of  lead  subacetate  it  is  white.  Kugles  gives  it  the  formula 
Pb(CN)OH,  while  Erlenmeyer  designates  it  by  Pb(CN)2  2PbO. 

CYANIDE  OF  COPPER,  Cu2(CN)2  =  178. 

fC  =13.49 

100Cu2(CN)2=  |  N  =15.73 
u  =  70.78 


100.00 

Cuprous  cyanide,  Cu2(CN)2,  only  is  stable.  It  is  a  white  powder 
which  is  precipitated  by  the  action  of  hydrocyanic  acid  on  an  hydro- 
chloric acid  solution  of  cuprous  chloride 

CYANIDE  OF  MERCURY,  Hg(CN)2=252. 

fC    =  9.52 

100Hg(CN)2=  |N   =11.11 
lHg  =  79.37 

100.00 

Mercuric  cyanide,  Hg(CN)2,  only  ,is  known.  It  crystallizes  in 
opaque,  colorless  prisms  soluble  in  water,  insoluble  in  alcohol.  It  is 
prepared  by  dissolving  mercuric  oxide  in  hydrocyanic  acid,  or  by 
boiling  one  part  of  potassium  ferrocyanide,  two  parts  of  mercuric 
sulphate,  with  eight  parts  of  water.  It  is  decomposable  by  heat,  con- 
centrated acids,  bromine,  iodine,  and  chlorine  (under  the  influence 
of  solar  rays).  It  is  very  poisonous. 

CYANIDE  OF  SILVER,  Ag(CN)  =  134. 

fC    =  8.96 

100Ag(CN)=  \  N  =10.44 
[Ag  =  80.60 

100.00 

It  is  a  white  substance,  closely  resembling  silver  chloride.  It  is 
obtained  by  precipitating  a  solution  of  silver  nitrate  with  potassium 
cyanide.  It  is  soluble  in  ammonia,  and  in  hot,  concentrated  nitric 
acid,  and  in  the  alkali  cyanides  and  chlorides. 


CHEMICAL  AND  PHYSICAL  STUDY.  27 

CYANIDE  OP  COBALT,  Co(CN)2  =  lll. 

rC   =21.63 

100Co(CN)2=  \  N  =25.22 
I  Co  =  53.15 


100.00 

Cobaltous  cyanide,  Co(CN)2,  is  a  flesh-colored  precipitate,  ob- 
tained by  precipitation  of  a  cobalt  salt  with  potassium  cyanide. 
Oxygen  of  the  atmosphere  changes  it  rapidly. 

CYANIDE  OF  NICKEL,  Ni(CN)2=»lll. 

rC  =21.63 
100Ni(CN)a=     N  =25.22 


100.00 

It  is  an  apple-green  substance  obtained  by  precipitating  a  salt 
of  nickel  with  potassium  cyanide,  or  by  the  action  of  hydrocyanic 
acid  on  nickel  acetate.  It  crystallizes  with  3  molecules  of  water. 

CYANIDE  OF  GOLD,  Au(CN)=222. 

C    =  5.41 

lOOAu(CN)  =  -j  N   =  6.31 
Au  =  88.28 


100.00 

Aurous  cyanide,  Au(CN),  is  a  beautiful  pale-yellow  crystalline 
powder,  very  stable,  insoluble  in  water,  alcohol,  and  acids:  It  is 
odorless  and  tasteless.  Heat  decomposes  it  into  cyanogen  and  gold. 
Boiling  potash  decomposes  it  slowly  into  potassium  gold  cyanide 
and  metallic  gold,  soluble  in  ammonium  sulphydrate,  ammonia, 
and  sodium  hyposulphite. 

CYANIDE  OF  PLATINUM,  Pt(CN)2=249. 

rC  =  9.64 

100Pt(CN)2=  \  N  =11.24 
I  Pt- 79,12 

100.00 

• 

Platinous    cyanide,    Pt(CN)2,   is   greenish   yellow,   insoluble  in- 


28  THE  CHEMISTRY  OF  CYANOGEN. 

water,  acids;  and  alkalis.    It  burns  in  air,  leaving  a  residue  of  me- 
tallic platinum. 

DOUBLE  CYANIDES. 

Most  of  the  cyanides  are  capable  of  combining  together  to  form 
double  cyanides.  Often  they  are  produced  by  dissolving  a  simple 
insoluble  cyanide  in  a  soluble  alkali  cyanide. 

There  are  two  classes  of  double  cyanides,  the  stable  and  the 
unstable. 

The  unstable  double  cyanides  are  decomposed  by  dilute  acids, 
when  the  insoluble  cyanide  is  precipitated  and  hydrocyanic  acid 
set  free;  the  gas  set  free  results  from  the  action  of  the  acid  used 
on  the  existing  alkali  cyanide. 

The  stable  cyanides,  on  the  other  hand,  resist  the  action  of  dilute 
acids.  In  this  case  there  is  only  a  substitution  of  the  hydrogen  for 
the  potassium  (potassium  cyanide  is  the  one  usually  employed) , 
and  there  is  formed  a  double  cyanide  of  hydrogen  and  heavy  metal. 

Salt  solutions  of  nearly  all  metals,  acting  on  double  cyanides, 
produce  the  phenomenon  of  double  decomposition. 

On  account  of  these  differences,  the  unstable  cyanides  are  generally 
considered  as  true  double  cyanides,  i.e.,  formed  by  two  simple 
cyanides,  while,  on  the  other  hand,  the  stable  cyanides  are  the  result 
of  the  union  of  an  alkali  metal  with  the  radical  formed  when 
cyanogen  combines  with  the  heavy  metal. 

This  hypothesis  seems  to  be  verified  from  the  following:  In  the 
stable  double  cyanides  the  heavy  metal  (by  heavy  metal  is  meant 
all  metals  except  alkali  arid  alkaline  earth  metals)  cannot  be  re- 
leased by  its  ordinary  reactions;  moreover,  hydrogen  may  be  sub- 
stituted for  the  alkali  metal;  besides,  they  are  neutral  and  non- 
poisonous.  On  the  con  rary,  in  the  unstable  double  cyanides  hydrogen 
cannot  be  substituted  for  the  alkali  metal,  and  the  heavy  metal  and 
even  the  cyanogen  are  more  easily  recognized  by  their  reagents. 

The  necessity  of  expressing  the  special  stability  of  one  of  the  two 
classes  of  these  compounds  has  caused  them  to  be  designated  by 
special  names:  ferro-,  ferri-,  cobalto-,  chromo-,  chromi-,  platino- 
cyanide,  etc.  Among  the  double  cyanides,  only  the  most  important 
will  be  studied,  and  first  among  these  the  f errocyanides  and  the  f  erri- 
cyanides. 


CHEMICAL  AND  PHYSICAL  STUDY.  29. 

FERROCYANIDES. 

FERROCYANIDE  OP  POTASSIUM,  Fe(CN)6K4  =  368. 
Ferrocyanide  of  potassium  has  the  following  composition: 

(•Fe  =15.22 

100Fe(CN)6K4  =  j  CN  =  42.39 
IK   =42.39 


100.00 

This  salt,  which  is  also  called  ferrocyanhydrate,  cyanoferride> 
double  cyanide  of  iron  and  of  potassium,  hydroferrocyanate,  yellow 
prussiate  of  potash,  corresponds  to  the  formula  Fe(CN)6K4.  It 
crystallizes  with  3  molecules  of  water  in  voluminous  monoclinic 
prisms.  It  has  a  citron-yellow  color,  is  flexible,  vitreous,  and  pos- 
sesses a  salty,  bitter  taste.  Its  density  is  1.833.  At  60°  C.  it  loses. 
its  water  of  crystallization,  which,  however,  does  not  completely 
disappear  except  at  100°  C.  It  is  then  converted  into  a  white 
powder.  It  is  soluble  in  water,  which  dissolves  two  parts  in  cold 
and  four  in  hot  water.  Its  aqueous  solution  saturated  at  15°  C. 
has  a  density  of  1.444. 

In  absence  of  air  it  fuses  just  below  red  heat  with  the  produc- 
tion of  nitrogen,  potassium  cyanide,  and  iron  carbide: 

Fe(CN)  6K4  =  FeC2  +  4CNK + N2. 

In  contact  with  air,  potassium  cyanate  and  peroxide  of  iron 
are  formed. 

When  burned  in  the  presence  of  an  alkali  it  is  entirely  con- 
verted into  cyanide  of  potassium: 

Fe(CN)6K4  +  K2C03  =  6CNK  +  FeO  +  C02. 

These  various  reactions  are  of  great  importance  and  are  utilized,, 
as  will  be  seen  more  in  detail  later,  in  the  industrial  manufacture  of 
cyanides 

Oxygen  exerts  no  action  on  ferrocyanide  of  potassium,  but  ozone, 
the  electric  current,  chlorine,  bromine,  dilute  nitric  acid,  peroxide  of 
lead,  manganese  dioxide,  permanganate  of  potash,  all  transform 
it  either  wholly  or  in  part  into  potassium  ferricyanide.  These 
various  reactions  may  be  expressed  thus: 


30  THE  CHEMISTRY  OF  CYANOGEN. 

With  chlorine, 

2[Fe(CN)6K4] + C12  =  Fe2(CN)  12K6 + 2KC1. 
With  the  electric  current, 

2[Fe(CN)6K4]  +  2H20  =  2KOH  +  H2 + Fe2(CN)  i2K6. 

These  two  reactions  are  used  industrially  in  the  preparation 
of  ferricyanide  of  potassium. 

Sulphur  converts  it  into  sulphocyanate.  When  ferrocyanide  of 
potassium  is  treated  with  dilute  sulphuric  acid  there  is  formed 
hydroferrocyanic  acid: 

[Fe(CN)6K4] +2H2S04  =  2K2S04 +Fe(CN)6H4. 
To  hydroferrocyanic  acid  Friedel  attributes  the  following  formula: 

NH 

II 
C 

•N=C/\C=NH 

I        | 
•N=C\/C=:NH 

II 
NH 

With  concentrated  sulphuric  acid  there  is  formed  carbon  mon- 
oxide, sulphates  of  iron,  potassium,  and  ammonium: 

Pe(CN)6K4 + 6H2S04  +  6H20  =  6CO  +  FeS04  +  2K2S04  +  3(NH4)  2S04. 

This  reaction  is  explained  as  follows :  The  sulphuric  acid  is  com- 
bined with  iron  and  potassium  sulphates;  hydrocyanic  acid  in  pres- 
ence of  moisture  has  yielded  ammonium  formate,  which,  acted 
upon  by  sulphuric  acid,  is  converted  into  ammonia  and  carbon 
monoxide. 

The  ammonia  thus  formed  unites  with  sulphuric  acid  to  form 
sulphate  of  ammonia,  while  the  carbon  monoxide  is  set  free. 

The  other  alkali  ferrocyanides  of  sodium  and  ammonium  have 
similar  properties.  They  are  soluble  in  water,  insoluble  or  only 
slightly  soluble  in  alcohol. 


CHEMICAL  AND   PHYSICAL  STUDY.  31 

Ferrocyanide  of  sodium,  Fe(CN)6Na4-f  12H20,  has  been  pro- 
posed as  a  substitute  for  ferrocyanide  of  potassium,  but  so  far  it 
has  no^  been  possible  to  use  it  industrially  on  account  of  the  enor- 
mous quantity  of  water  of  crystallization  which  it  contains  and 
which  renders  its  transportation  much  more  expensive. 

The  alkaline-earth  ferrocyanides  are  white  and  insoluble. 

The  other  metallic  ferrocyanides  have  various  colors,  which  are 
frequently  used  in  chemical  analyses. 

The  most  interesting  are  those  of  barium,  which  are  white  and 
very  soluble ;  the  cuprous  salt,  which  is  red,  and  the  cupric,  which  is 
white;  the  nickel,  which  is  greenish  white,  and  the  lead,  which  is 
white. 

Ferrocyanide  of  iron  is,  among  these  latter,  very  interesting;  the 
ferriferrocyanide  is  more  generally  known  under  the  name  Prussian 
blue: 

[Fe(CN)6]3Fe4  +  18H20. 

This  Prussian  blue  is  formed  by  the  action  of  a  ferric  salt  on 
potassium  ferrocyanide : 

3Fe(CN)6K4 +2Fe2Cl6  =  (Fe(CN)6)3Fe4  +  12KC1. 

It  is  a  dark-blue  powder,  odorless  and  insipid.  Its  fracture  has  a 
copper-like  lustre.  It  loses  its  water  of  crystallization  completely 
only  when  decomposed. 

It  is  insoluble  in  water,  alcohol,  ether,  and  weak  acids.  It  is 
soluble  in  ammonium  tartrate  and  in  oxalic  acid,  giving  a  violet 
solution  in  the  former  case  and  a  blue  solution  in  the  latter. 

When  burned  it  yields  carbonic  acid,  and  water,  and  carbonate 
and  cyanhydrate  of  ammonia. 

When  treated  with  concentrated  sulphuric  acid  it  is  converted 
into  a  white  pitchy  mass,  which  on  the  addition  of  water  is  recon- 
verted into  Prussian  blue.  It  is  but  slowly  affected  by  hydro- 
chloric acid.  Potassium  hydroxide  converts  it  into  ferric  hydrate 
and  potassium  ferrocyanide.  This  reaction  is  utilized  in  the  manu- 
facture of  potassium  ferrocyanide  extracted  from  the  purifying 
materials  of  illuminating-gas. 

The  alkali  carbonates  act  in  the  same  way,  but  less  easily. 


32  THE  CHEMISTRY  OF  CYANOGEN. 

Soluble  Prussian  blue  is  the  name  given  to  the  compound  formed 
by  the  union  of  ordinary  Prussian  blue  with  f  errocyanide  of  potassium* 

FERRICYANIDES. 

Beside  the  ferrocyanides  is  placed  another  class  of  double  cyan- 
ides which  is  derived  from  them — the  ferricyanides.  Ferricyanides 
may  be  considered  as  double  ferrocyanides  minus  2  atoms  of  metal: 

2Fe(CN)6K4-K2  =  Fe2(CN)12K6. 

The  tetratomic  ferrocyanogen  radical,  Fe(CN)6,  uniting  with 
itself  by  exchanging  two  valences,  is  transformed  into  the  hexatomic 
radical  Fe2(CN)i2-  Various  authors  consider  the  ferricyanides  as 
double  cyanides  of  ferric  iron  with  another  metal;  others,  on  the 
other  hand,  think  that  they  result  from  the  union  of  a  metal  with 
the  radical  Fe2(CN)i2. 

The  following  ferricyanides  are  known:  Potassium,  red;  silver, 
orange;  barium  and  potassium,  black;  calcium,  gold  color;  cobalt, 
red;  copper,  yellow;  nickel,  greenish  yellow. 

The  ferricyanides  of  the  alkalis  and  of  the  alkaline  earths  only 
are  soluble;  the  others  are,  as  a  rule,  insoluble. 

The  most  interesting  is  ferricyanide  of  potassium,  also  called 
cyaniferride,  red  prussiate  of  potash.  The  discovery  of  this  salt 
was  made  by  Gmelin.  Its  percentage  composition  is  as  follows: 

fFe  =17.02 

100Fe2(CN)12Ka=  |  CN  =  47.42 
[K   =35.56 

100.00 

It  occurs  as  red  rhombic  anhydrous  prisms,  having  a  density 
of  1.800  to  1.845  according  to  different  investigators.  It  has  a 
salty  taste,  is  soluble  in  water,  especially  so  in  hot  water.  At  4.4°  C. 
one  part  of  the  salt  is  soluble  in  3.03  parts  water,  yielding  a  solution 
whose  sp.  gr.  is  1.151.  At  104°  C.  1.22  parts  water  dissolve  one 
part  salt;  the  solution  then  has  a  density  of  1.265. 

Dilute  solutions  of  f  errocyanide  are  orange-yellow;  concen- 
trated solutions  are  yellowish-brown.  A  solution  of  ferricyanide 
is  decomposed  in  the  light  and  on  boiling,  ferrocyanide  being  formed. 


CHEMICAL  AND  PHYSICAL  STUDY.  33 

It  is  precipitated  from  its  solutions  of  alcohol.  Under  the  influ- 
ence of  heat  it  crackles,  and  is  converted  into  ferrocyanide, 
nitrogen,  cyanogen,  Prussian  blue,  paracyanogen,  and  iron 
carbide. 

When  burned  in  the  flame  of  a  candle  it  emits  sparks  of  iron. 

Electrolysis  and  reducing  agents,  such  as  hydrogen  sulphide, 
convert  it  into  ferrocyanide: 

2Fe2(CN)  i2K6  +  2H2S  =  3Fe(CN)  6K4  +  Fe(CN)  6H4  +  2S. 

Nitric  acid  converts  it  into  nitrate  and  nitroprusside  of  potassium. 
Bed  prussiate  peroxidizes  the  greater  part  of  metallic  oxides. 

Hydrochloric  acid  decomposes  a  solution  of  ferricyanide  of 
potassium,  transforming  it  into  ferricyanide  of  iron. 

When  treated  with  ammonia  it  yields  ferrocyanide  of  potassium 
and  of  ammonium  and  nitrogen.  It  oxidizes  phosphorus,  sul- 
phur, sulphurous  acid,  and  sulphites;  it  converts  oxalic  acid  and 
oxalates  into  carbonates.  Organic  substances  in  general,  and 
especially  in  the  presence  of  ferric  salts,  likewise  exert  a  reducing 
action  on  ferricyanide  of  potassium.  All  these  reactions  are  very 
easily  carried  out  if  one  operates  in  alkaline  solutions. 

When  a  solution  of  a  ferrous  salt  is  treated  with  potassium  ferri- 
cyanide a  beautiful  blue  precipitate  is  obtained,  which  is  called 
Turnbull's  blue,  Fe5(CN)i2+zH20.  This  blue  is  distinguished 
from  Prussian  blue  in  that  when  it  is  heated  with  carbonate  or 
hydrate  of  potassium  it  yields  ferroferric  hydrate  and  yellow  prus- 
siate, while  Prussian  .  blue  under  the  same  conditions  yields  ferric 
hydrate  : 

Fe5(CN)i2  +8KOH=  2[Fe(CN)6K4]  +Fe3(OH)8 


Just  as  there  is  to  the  ferrocyanides  a  corresponding  acid,  hydro- 
ferrocyanic  acid,  so  to  the  ferricyanides  there  is  a  corresponding 
acid,  hydroferricyanic  acid,  Fe2(CN)i2H6,  which,  according  to 
Friedel,  may  be  represented  by  the  following  formula: 


HN=C        O=N  v  >     N=C 


HN=C        C=N  N=CC=NH 


34  THE  CHEMISTRY  OF  CYANOGEN. 

Among  the  other  interesting  double  cyanides  must  be  mentioned 
the  cobalticyanides,  mangano-  and  manganicyanides,  and  finally 
the  platino-  and  platinicyanides. 

COBALTICYANIDES. 

Cobaltocobalticyanide  is  similar  to  TurnbulPs  blue.  Hydro- 
cobalticyanic  acid  is  quite  energetic,  capable  of  decomposing  car- 
bonates, of  dissolving  iron  and  zinc,  setting  free  hydrogen,  and 
of  neutralizing  alkali  bases.  The  most  interesting  of  the  cobalti- 
cyanides are  those  of  potassium,  C02(CN)i2K6,  an  anhydrous  salt, 
pale  yellow,  slightly  soluble  in  water,  insoluble  in  alcohol;  of  cop- 
per, Co2(CN)i2Cu3  +  7H20,  clear  blue,  insoluble  in  water  and  in  acids, 
soluble  in  ammonia.  The  cobalticyanide  of  nickel,  Co2(CN)i2Ni3  + 
2H20,  blue  when  moist,  green  when  dry,  insoluble  in  water  and 
acids,  soluble  in  ammonia. 

The  cobalticyanides  are  not  toxic;  they  are  in  all  respects  analo- 
gous to  ferricyanides. 

MANGANOCYANIDES. 

Manganocyanides  are  very  unstable  in  air,  which  converts  them 
into  manganicyanides,  which  are  likewise  easily  decomposable.  Their 
solution  is  stable  only  in  the  presence  of  potassium  cyanide. 

PLATINOCYANIDES. 

Platinocyanides  correspond  to  the  general  formula  Pt(CN)6M2. 
They  may  be  considered  either  as  combinations  of  cyanide  of  plati- 
num with  a  basic  cyanide,  or  as  the  result  of  the  union  of  a  metal 
with  the  diatomic  radical  Pt(CN)e. 

Soluble  platinocyanides  are  obtained  by  dissolving  platinocy- 
anide  hi  an  alkali  cyanide,  or  else  by  precipitating  platinous  chloride 
with  pot  ssium  cyanide.  The  other  platinocyanides  are  obtained 
by  double  decomposition. 

Platinicyanides  are  obtained  by  the  action  of  oxidizing  agents 
on  platinocyanides.  Their  mode  of  formation  is  doubtful;  at  present 
the  best  hypoth  sis  known  is  that  of  Hadow,  who  considers  the  platini- 
cyanides as  a  union  of  the  platinocyanide  with  the  oxidizing  agent 
used  in  obtaining  them. 


'  CHEMICAL  AND  PHYSICAL  STUDY.  35 

AUROCYANIDES. 

More  stress  will  be  laid  on  the  double  cyanides  of  gold,  or  auro- 
cyanides,  on  account  of  the  impetus  which  they  have  given  to  the 
cyanide  industry.  Aurous  cyanide  unites  easily  with  the  cyanides 
of  the  other  metals,  yielding  double  cyanides,  among  which  may 
be  cited: 

(1)  Aurosoammonium  cyanide,  Au(CN)2NH4,  obtained  by  mixing 
saturated  solutions  of  ammonium  sulphite  with  auricopotassic  cyanide. 
It  is  readily  soluble  in  water  and  in  alcohol.    It  is  decomposed  be- 
tween 200°  and  250°  C. 

(2)  Aurosopotassic     cyanide,    or     aurocyanide    of     potassium, 
Au(CN)2K,  obtained  by  dissolving  cyanide  of  gold,  oxide  of  gold, 
or  fulminating  gold  in  potassium  cyanide.     It  crystallizes  in  mother- 
of-pearl  scales,  is  anhydrous,  colorless,  has  a  salty  taste,  is  stable  in 
air,  soluble  in  7  parts  cold  water,  more  soluble  in  boiling  water, 
slightly  soluble  in  alcohol,  insoluble  in  ether.     It  is  decomposed  in 
a  closed  vessel,   setting   cyanogen  free,  and  leaving '  a  residue  of 
potassium  cyanide  and  gold.     Acids  break  it  up  into  aurous  cyanide. 

Auricopotassic  cyanide,  or  auricyanide  of  potassium,  Au(CN)4K, 
occurs  as  large  colorless,  efflorescent  crystals  capable  of  being  fused 
into  a  liquid  which  sets  cyanogen  free  and  leaves  behind  metallic  gold. 

NITROPRUSSIATES 

Nitroprussiates,  or  nitroferricyanides,  are  obtained  when  nitric 
acid  acts  on  the  ferro-  or  ferricyanides.  According  to  Gerhardt, 
the  formation  of  these  compounds  is  due  rather  to  the  action  of 
nitrogen  dioxide  which  is  formed  by  the  nitric  acid. 

This  author  ascribes  to  them  the  following  formula :  Fe(CN)  5(NO)M2 
or  Fe2(CN)io(NO)2M4.  They  are  non-saturated  ferrocyanides,  of 
which  the  radical  CN  is  replaced  by  NO,  or  may  be  considered  as 
ferricyanides  where  2  (NO)  replaces  the  group  2(CN)M. 

These  salts  are  generally  highly  colored.  Those  of  potassium, 
sodium,  ammonium,  barium,  calcium,  and  lead  are  dark  red,  readily 
soluble,  and  distinctly  cystaUine;  those  of  copper,  silver,  zinc,  iron, 
and  nickel  are  insoluble.  Alkalis  decompose  them,  likewise  does 
concentrated  sulphuric  acid;  some  of  them  dissolve  Prussian  blue. 
They  give  with  sulphides  purple  color  which  is  little  stable.  On 
heating  them,  nitrosulphides  are  produced. 


•36  THE  CHEMISTRY  OF  CYANOGEN. 

OXYGEN  COMPOUNDS  OF  CYANOGEN. 

CYANIC  ACID,  CNOH  =  43. 
[  C= 27.90 

100CNOH=     J:gJ 

H-  2.33 

100.00 

Cyanic  acid  is  an  oxygen  compound  of  cyanogen,  which  was 
discovered  in  1818  by  Vauquelin,  later  studied  by  Woehler  and 
Liebig. 

Its  formula  is  CNOH.  It  is  monatomic.  It  is  a  colorless  liquid, 
'with  sharp  odor,  the  vapors  of  which  irritate  the  eyes  decidedly. 
It  is  soluble  in  water,  but  its  solution  readily  breaks  up  into  car- 
bonic acid  and  ammonia.  Its  solution  in  ether  is  the  only  one 
which  is  stable.  When  its  alcoholic  solution  is  heated  it  yields 
asters  of  allophanic  acid. 

With  metals  it  produces  cyanates,  salts  which  are  quite  stable 
when  dry,  except  copper,  mercury,  and  silver  cyanates,  but  the 
presence  of  moisture  breaks  them  up  into  carbonate  and  ammonia: 

2CNOM + 3H20  =  M2C03  +  2NH3 + C02. 

They  are,  as  a  rule,  soluble.  The  cyanates  of  copper,  mercury,  and 
silver  are  only  slightly  soluble. 

Dilute  acids  decompose  them  into  cyanic  acid,  but  quite  often 
into  carbonic  acid  and  ammonia.  With  concentrated  acids,  cyam- 
elide  is  formed. 

The  alkali  cyanates  are  obtained  by  igniting  in  air  the  corre- 
sponding cyanides,  especially  in  the  presence  of  metallic  oxides,  as, 
e.g.,  oxide  of  lead,  manganese,  or  copper. 

CYANATE  OF  POTASSIUM,  CNOK=81. 
C  =  14.81 

100CNOK=     5:j™ 

K  =  48.14 

100.00 

Cyanate  of  potassium  occurs  as  transparent  anhydrous  crystals, 
soluble  in  water.  It  is  obtained,  generally,  by  heating  manganese 
dioxide  with  potassium  ferrocyanide  to  redness. 


CHEMICAL  AND  PHYSICAL  STUDY.  37 

It  is  gradually  decomposed  by  moist  air  and  by  water  into 
carbonate  of  potassium  and  ammonium. 

Potassium  dissolves  in  melted  cyanate,  yielding  cyanide  and 
oxide.  Cyanate  of  sodium,  CNONa,  has  analogous  properties. 

Cyanate  of  ammonium  is  an  isomer  of  urea,  which  it  yields  when 
heated  at  a  moderate  temperature,  CNOH-NH3. 

Silver  cyanate  is  white,  readily  soluble  in  ammonia  and  dilute 
nitric  acid.  When  heated  it  explodes  rather  violently,  leaving  a 
residue  of  silver  carbide. 

CYANUEIC  ACID  AND  TRICYANATES. 

Cyanuric  acid  was  discovered  by  Scheele  and  studied  successively 
by  Serullas,  Woehler,  and  Liebig.  It  is  obtained  in  many  reac- 
tions, but  the  best  method  of  producing  it  is  that  of  Wurtz,  which 
consists  in  passing  dry  chlorine  through .  melted  urea  and  treating 
the  residue  successively  with  cold  and  with  boiling  water.  It  is 
a  solid,  crystallizing  in  octahedrons,  odorless,  tasteless,  readily 
soluble  in  water,  alcohol,  and  concentrated  mineral  acids.  It  is 
acid  in  reaction.  It  volatilizes  at  360°  C.,  when  it  is  converted  into 
cyanic  acid.  By  prolonged  boiling  with  concentrated  acids  it 
breaks  up  into  carbonic  acid  and  ammonia. 

With  metals  it  yields  tricyanates,  which  are  only  slightly  soluble. 
They  are  decomposed  by  strong  acids  which  set  cyanuric  acid  free. 
When  the  tricyanates  are  heated  they  are  converted  into  cyanates. 

SULPHOCYANIDES. 

Sulphocyanides,  or  rhodanides  as  they  are  sometimes  called,  are 
really  sulphocyanates.  They  are  formed  by  the  union  of  sulpho- 
cyanic  acid  with  a  metal.  This  sulphocyanic  acid  is  really  cyanic 
acid  in  which  the  oxygen  has  been  replaced  by  sulphur: 

CNOH,        CNSH. 

For  a  long  time  it  was  wrongly  considered  as  a  hydrazid  of  the  com- 
plex sulphocyanogen  radical  (CN)S. 

The  sulphocyanides  have  the  general  formula  (CN)SM.  Most 
of  them  are  soluble  in  water,  alcohol,  and  ether,  especially  those 
of  the  alkali  metals.  They  easily  form  double  salts.  As  to  the 


38  THE  CHEMISTRY  OF  CYANOGEN. 

sulphocyanides  of  the  heavy  metals,  they  are  insoluble,  but  are 
decomposed  on  boiling  with  the  alkalis.  Dilute  acids  decompose 
them  even  in  the  cold,  with  the  exception  of  those  of  silver,  mercury, 
and  copper.  In  acid  solution  they  are  oxidized  by  permanganate 
of  potash  into  hydrocyanic  acid  and  sulphuric  acid. 

Among  the  many  sulphocyanides  only  the  most  important  will 
be  studied. 

SULPHOCYANIDE   OF   POTASSIUM,  CNSK  =  97. 

f  C  =  12.37 

100(CN)SK-  j  *:£JJ 
IK  =  40.20 


100.00 

This  is  an  anhydrous,  extremely  deliquescent  salt,  crystallizing 
in  prisms  or  in  needles,  of  a  density  1.886  to  1.906,  very  soluble  in 
water  and  in  alcohol  (100  parts  water  dissolve  130  parts).  Its 
solution  in  water  is  accompanied  by  an  appreciable  lowering  of 
temperature  (150  parts  of  this  salt  dissolved  in  100  parts  of  water 
at  11°  C.  cause  a  temperature  of.  —23°  C.).  It  has  a  fresh  and  pun- 
gent taste,  but  it  is  not  poisonous.  According  to  physiologists,  it 
occurs  in  the  human  saliva. 

When  ignited  in  air  it  is  converted  into  potassium  sulphate, 
though  it  is  capable  of  withstanding  a  dull  red  heat  for  a  long  time 
without  decomposition. 

Its  aqueous  solution  undergoes  a  slow  decomposition,  which  may 
be  hastened  by  application  of  heat.  Ammonia  is  set  free. 

Chlorine  and  nitric  aoid  decompose  it.  When  heated  with  a 
metal,  potassium  cyanide  and  a  metallic  sulphide  are  formed: 

CNSK+Fe  =  CNK+FeS. 

This  reaction  has  been  used  as  a  means  of  obtaining  the  alkali- 
cyanides. 

Sulphocyanide  of  sodium,  (CN)SNa,  has  analogous  properties. 

Sulphocyanide  of  ammonium,  (CN)SNH4,  occurs  in  the  form  of 
deliquescent  prisms  readily  soluble  in  alcohol  and  in  water  (105 
parts  in  100  water).  A  mixture  of  133  parts  of  this  salt  with  100 


CHEMICAL  AND  PHYSICAL  STUDY.  39 

parts  of  water  at  13°  C.  causes  a  lowering  of  31°  in  temperature. 
It  melts  at  159°  C.,  and  when  heated  to  170°  C.  it  becomes  trans- 
formed into  sulphocarbamide : 

NH2  or  thiourea. 
NH2. 

When  subjected  to  dry  distillation  it  is  decomposed,  yielding 
hydrogen  sulphide,  and  sulphides  of  carbon  and  ammonia,  leaving 
a  residue  of  melam.  It  is  capable  of  dissolving  salts  of  sulphur. 

Silver  sulphur  cyanide  is  a  white  curdy  precipitate,  insoluble  in 
water  and  ammonia,  soluble  in  the  sulphocyanides  of  ammonia  and 
of  potassium. 

ORGANIC  COMPOUNDS. 

By  substitution  of  the  group  CN  for  OH  hydrocyanic  acid  is 
capable  with  alcohols  of  forming  hydrocyanic  esters,  which  may 
be  divided  into  two  classes.  In  the  first  class,  the  alcoholic  radical 
is  attached  to  the  carbon;  in  the  second,  it  is  attached  to  the  nitro- 
gen. These  are  isomeric  bodies;  the 'former  are  called  nitriles  and 
correspond  to  the  general  formula  R— C  =  N;  the  latter  are  carbyl- 
amines  or  isonitriles,  their  formula  being  represented  by  R— N  =  C. 
These  are  rather  interesting  bodies  which  should  not  be  overlooked. 

NITRILES   AND    CARBYLAMINES. 

Nitriles  are  derived  from  amides  through  dehydration. 

Nitriles  possess  general  analogous  properties  whatever  may  be 
the  atomicity  of  the  alcohols  from  which  they  are  derived;  they 
form  a  clearly  defined  class  of  compounds. 

Nitriles  have  the  following  prope  ties 

Under  the  influence  of  nascent  hydrogen  they  fix  4  molecules 
of  this  element  and  form  primary  amines. 

Under  the  influence  of  dehydrating  agents  nitriles  fix  2  mole- 
cules of  water  and  are  converted  into  ammonia  salts  of  acids  con- 
taining the  same  number  of  carbon  atoms  as  the  hydrocyanic  acid 
ester  used.  Thus  methyl  cyanide  gives  ammonium  acetate. 

They  fix  likewise  one  molecule  of  hydrogen  sulphide  in  pro- 
ducing amido-sulphides.  They  unite  with  hydracids,  with  negative 
chlorides,  and  with  bromides. 


40  THE  CHEMISTRY  OF  CYANOGEN. 

The  lowest  member  of  the  nitrile  series  is  hydrocyanic  acid,  or 
formonitrile,  H—  C=N.  Among  the  most  important  may  be  cited: 

Methyl  cyanide,  or  acetonitrile,  CH3CN,  a  colorless  liquid,  lighter 
than  water  (sp.  gr.  0.81-0.83),  volatilizing  at  77-78°  C.,  having  a 
pungent,  aromatic,  and  ether-like  odor.  It  is  obtained  by  distilling 
ammonium  acetate  with  anhydrous  phosphoric  acid. 

Ethyl  cyanide  or  propionitrile,  C2H5CN,  is  a  colorless  liquid 
having  an  alliaceous  odor,  sp.  gr.  0.78,  boiling-point  96.5°  C. 

Propyl  cyanide,  or  but  yronit  rile,  CH3  •  CH2  •  CH2CN,  having  a 
density  of  0.79  and  boiling  at  116°  C. 

Butyl  cyanide,  C4H9CN,  density  0.816,  boiling-point  126°  C.; 
amyl  cyanide,  C5HuCN;  allyl  cyanide,  CH2  :  CH  •  CH2  •  CN,  density 
€.839,  boiling-point  118°  C.;  cetyl  cyanide,  Ci6H33CN. 

The  properties  of  the  hydrocyanic  esters  of  the  second  class,  or 
carbylamines,  are  quite  different  from  those  of  the  nitriles.  They 
are  generally  formed  by  the  action  of  alkyl  iodides  on  silver  cyanide  : 


Carbylamines  are  distinguished  from  nitriles,  their  isomers,  by 
their  odor,  which  is  often  disgusting,  by  their  higher  boiling-point, 
by  their  property  of  combining  directly  with  acids,  and  finally 
by  the  action  which  hydrating  and  oxidizing  agents  produce  upon 
them. 

In  this  case  they  yield,  as  do  the  nitriles,  two  products,  one 
fixed,  the  other  variable,  according  to  the  ester  employed.  But 
here  the  fixed  product  is  no  longer  ammonia,  and  the  variable  product 
an  acid  more  or  less  rich  in  carbon.  The  first  is  always  formic  acid, 
while  the  latter  is  an  ammonium  compound.  Thus  methylcarbyl- 
amine,  ethylcarbylamine,  amylcarbylamine  yield,  respectively,  with 
hydrating  agents,  by  fixing  2  molecules  of  water,  methylamine,  ethyl- 
amine,  and  amylamine. 

CYANIC   ESTERS. 

By  its  union  with  alcohol  radicals,  cyanic  acid  also  yields  cyanic 
esters,  or  alcoholic  carbimides.  The  following  only  will  be  men- 

(CO 
n  TT  ,  methyl  cyanate,  and  butyl  cyanate. 
^2^15 

These  are  mobile  liquids,  possessing  repulsive  odors  and  high  boil- 


CHEMICAL  AND  PHYSICAL  STUDY  41 

ing-points.  Potash  converts  them  into  primary  amines.  It  is  ta 
Wurtz  that  we  owe  the  discovery  and  study  of  these  bodies.  But 
these  are  not  true  cyanic  esters. 

The  true  yanic  esters  were  discovered  by  Cloez.  They  are 
isomeric  with  the  esters  discovered  by  Wurtz,  but  with  this  differ- 
ence, that  under  the  influence  of  hydrating  agents  they  no  longer 
yield  amines  a,;jd  carbonic  acid  as  do  the '  carbimides,  but  behave 
themselves  as  ordinary  esters  and  yield  the  same  alcohol  as  was 
used  at  the  start,  and  a  cyanate  or  tricyanate.  Their  density  is. 
also  somewhat  higher. 


CHAPTER  III. 

GENERAL  PROPERTIES  AND  METHODS  OF   DETERMINATION 
OF  THE  VARIOUS  CYANIDE  COMPOUNDS. 

I.  ANALYTICAL  PROPERTIES. 

HYDROCYANIC    ACID. 

THE  analytical  properties       hydrocyanic  acid  are  the  following: 

Silver  nitrate :  White  precipitate  soluble  in  ammonia  and  in 
boiling  nitric  acid.  Iron  s  ts  in  the  presence  of  alkalis:  By  adding 
potash  and  a  few  drops  of  a  ferrous  and  a  ferric  salt  to  a  hydro- 
cyanic acid  solution  there  is  formed  a  precipitate.  If  this  be  treated 
with  hydrochloric  acid,  the  oxide  of  iron  dissolves,  and  the  liquid 
remains  dark  blue,  due  to  the  Prussian  blue  in  suspension. 

The  following  method  can  be  used  in  the  detection  of  even 
1/20ooth  part  of  hydrocyanic  acid:  To  the  liquid  to  be  tested, 
add  a  little  potash  and  a  small  amount  of  copper  sulphate.  This 
produces  a  precipitate  of  cyanide  and  hydrate  of  copper.  By  treat- 
ing this  precipitate  with  hydrochloric  acid  the  hydrate  dissolves, 
leaving  a  white  residue  of  copper  cyanide. 

Liebig  and  Taylor's  method  is  also  quite  delicate.  This  con- 
sists in  converting  hydrocyanic  acid  into  ammonium  sulphocy- 
anate,  by  heating  it  with  ammonium  sulphide  until  decolorized. 
On  adding  a  drop  of  a  ferric  salt  to  this  sulphocyanate  a  blood- 
red  coloration  is  produced. 

CYANIDES. 

Silver  nitrate  gives  a  white,  curdy  precipitate,  soluble  in  excess 
of  reagent,  soluble  in  ammonium  hydroxide,  insoluble  in  dilute 
nitric  acid.  On  igniting  silver  cyanide,  it  sets  free  cyanogen  gas, 
burning  with  a  purple  flame. 

Ferrous-ferric  salt  gives  a  dirty-green  precipitate  with    neutral 

42 


ANALYTICAL  PROPERTIES.  43 

solutions;  a  precipitate  of  Prussian  blue  and  a  ferrous-ferric  oxide 
in  alkaline  solution.  On  addition  of  an  acid  the  latter  dissolves, 
leaving  Prussian  blue.  Copper  sulphide  and  tincture  of  guaiacum, 
if  acidulated  with  a  drop  of  hydrochloric  acid,  give  an  intense  blue 
coloration. 

Acids  give  free  hydrocyanic  acid,  recognized  by  its  odor  of  bitter 
almonds. 

Calcium  chloride:  no  precipitate. 

Ammonium  sulphide  when  heated  with  cyanides  and  evaporated 
to  dry  ness,  gives  a  red  coloration  on  the  addition  of  a  ferric  salt. 

FERROCYANIDES. 

Calcium  chloride  gives  a  precipitate  in  concentrated  solutions. 
If  the  solution  to  be  tested  is  only  moderately  concentrated,  no 
precipitate  occurs.  Silver  nitrate  produces  a  reddish-brown  pre- 
cipitate insoluble  in  nitric  acid  and  in  ammonia. 

'  Ferrous  sulphate  produces  a  white  precipitate,  which  on  expo- 
sure to  the  air  rapidly  changes  to  blue  by  oxidation.  Chlorine 
and  nitric  acid  oxidize  this  precipitate  instantly. 

Ferric  chloride  gives  a  precipitate  of  Prussian  blue,  insoluble  in 
hydrochloric  acid,  but  decomposed  by  boiling  potash. 

Copper  sulphate  gives  a  brownish-red  precipitate  insoluble  in 
HC1. 

Concentrated  sulphuric  acid,  hot,  sets  free  pure  carbon  monoxide. 
If  the  acid  be  dilute,  hydrocyanic  acid  is  set  free. 

FERRICYANIDES. 

Silver  nitrate  gives  an  orange- yellow  precipitate  readily  soluble 
in  ammonia,  insoluble  in  nitric  acid. 
Calcium  chloride:  no  precipitate. 

Ferrous  sulphate  produces  a  blue  precipitate  insoluble  in  HC1. 
Ferric  chloride  yields  brown  coloration. 

Copper  sulphate  gives  greenish-yellow  precipitate  insoluble  in  HC1. 
Sulphuric  acid  gives  same  reactions  as  with  ferrocyanides. 

SULPHOCYANIDES. 

Silver  nitrate  gives  a  white  flocculent  precipitate,  soluble  in  excess 
of  the  reagent,  slightly  soluble  in  ammonia. 
Calcium  chloride:  no  precipitate. 


44  THE  CHEMISTRY  OF  CYANOGEN. 

Ferric  chloride  produces  a  blood-red  coloration,  stable  in  the  pres- 
ence of  HC1,  but  disappearing  when  exposed  to  heat  or  to  the  action 
of  nitric  acid,  sulphurous  acid,  hyposulphites,  or  alkalis. 

Copper  sulphate  and  sulphurous  acid  give  a  white  precipitate  of 
copper  sulphocyanide  insoluble  in  acids,  soluble  in  ammonia. 

Lead  acetate  produces  a  crystalline  precipitate  which  forms  quite 
slowly. 

Sulphuric  or  hydrochloric  acid  produces  no  effect  if  the  sulpho- 
cyanide solution  be  dilute  and  cold ;  at  the  end  of  some  time  a  yellow 
coloration  takes  place,  and  later  a  yellow  precipitate  of  persulpho- 
cyanic  acid;  in  warmth,  carbon  dioxide  is  set  free,  besides  sulphide 
of  carbon  and  hydrogen  sulphide. 

Dilute  nitric  acid  gives,  in  warmth,  a  yellow  deposit  of  persulpho- 
cyanogen. 

Molybdic  acid  dissolved  in  HCl  gives  a  red  coloration  which  may 
be  absorbed  by  ether. 

CYANATES. 

Silver  nitrate  produces  a  white  precipitate  which  can  be  decom- 
posed by  heat  and  is  soluble  in  ammonia  and  in  nitric  acid. 

Lead  acetate  gives  a  white  crystalline  precipitate  soluble  in  boiling 
water  (distinct  from  that  produced  in  hydrocyanic  solution). 

Dilute  and  cold  sulphuric  acid  yields  carbonic  acid  possessing  a 
pungent  odor  due  to  a  mixture  of  this  acid  with  non-decomposed 
cyanic  acid. 


II.  METHODS  FOR  THE  ANALYSES    OF  THE  VARIOUS  CYANIDE 

COMPOUNDS. 

CYANIDES. 

Liebig's  Method. — This  is  a  volumetric  method  based  on  the 
following  reactions:  If  to  a  solution  of  potassium  cyanide  is  added 
a  solution  of  silver  nitrate,  there  is  formed  silver  cyanide  soluble  in 
the  potassium  cyanide  still  remaining  in  the  solution.  Cyanide  of 
silver  is  formed  permanently  only  when  all  the  potassium  cyanide 
has  been  converted  into  the  double  cyanide.  The  appearance  of 
the  slightest  amount  of  a  permanent  precipitate  indicates  the  end 
of  the  reaction: 


ANALYTICAL  PROPERTIES.  45 

CNK+AgN03  =  CNAg+KN03, (1) 

CNK+CNAg=(CN)2KAg, (2) 

or 

2CNK+AgN03  =  (CN)2KAg+KN03. 

One  molecule  or  170  grams  of  silver  nitrate  requires  therefore  two 
molecules  or  130  grams  of  potassium  cyanide  to  form  one  molecule 
of  the  double  cyanide  of  silver  and  potassium.  A  solution  of  silver 
containing  13.056  grams  of  pure  silver  nitrate  per  liter  is  prepared, 
and  another  solution  containing  one  gram  of  potassium  cyanide  in 
100  cubic  centimeters  of  distilled  water  is  made,  of  which  10  cc. 
are  used.  Several  drops  of  a  solution  of  sodium  chloride  are  added, 
and  then  the  solution  of  silver  nitrate  is  run  in  drop  by  drop  until 
a  permanent  precipitation  is  formed.  Each  tenth  of  a  cubic  centi- 
meter of  the  silver  nitrate  used  corresponds  to  one  milligram  of 
potassium  cyanide.  Three  or  four  titrations  should  be  made  and 
the  average  taken. 

This  method  is  applicable  to  solutions  of  hydrocyanic  acid,  which 
must  first  be  saturated  with  potash. 

If  the  cyanide .  contains  chlorides,  the  method  is  not  accurate. 
In  this  case  the  gravimetric  method  is  preferable.  The  solution  of 
cyanide  is  precipitated  by  silver  nitrate,  the  precipitate  is  filtered, 
washed,  dried,  and  weighed.  Then  it  is  boiled  with  HC1,  which 
converts  the  silver  cyanide  into  silver  chloride.  This  is  filtered, 
washed,  dried,  and  weighed  again.  From  the  increase  in  weight  may 
be  calculated  the  quantity  of  cyanide.  1  gram  CNK  should  give 
2.058  grams  CNAg. 

Fordos  and  Gelis'  Method. — This  method  is  to  be  recommended. 
It  is  based  on  the  ability  of  potassium  cyanide  to  decolorize  a  solu- 
tion of  iodine  in  alcohol  or  in  potassium  iodide.  The  reaction  is 
as  follows:  CNK+I2  =  KI  +  CNL  That  is,  there  is  a  formation 
of  potassium  iodide  and  of  cyanogen  iodide,  both  of  which  are 
colorless.  The  end  of  the  reaction  is  indicated  by  the  yellow  colora- 
tion of  iodine  in  excess; 

The  iodine  solution  is  prepared  by  dissolving  40  grams  pure 
iodine  in  one  liter  alcohol  of  33°.  Five  grams  of  the  cyanide  to 
be  analyzed  are  dissolved  in  500  cc.  distilled  water.  50  cc.  of  this 


46 


THE  CHEMISTRY   OF  CYANOGEN. 


solution  are  transferred  to  a  2-liter  flask,  to  which  is  added  1 
liter  of  water  and  100  cc.  seltzer- water.  The  addition  of  this 
carbonated  water  converts  the  bases  and  carbonates  to  bicarbon- 
ates,  which  do  not  absorb  iodine.  Then  the  iodine  solution  is  added 
drop  by  drop,  stirring  constantly,  till  the  yellow  coloration  char- 
acteristic of  iodine  dissolved  in  potassium  iodide  appears. 

From  the  volume  of  iodine  solution  used  must  be  subtracted 
the  quantity  of  cyanide,  knowing  that  254  parts  of  iodine  are  absorbed 
by  65  parts  of  potassium  cyanide.  If,  at  the  end  of  the  titration, 
the  solution,  colored  by  several  drops  of  iodine  in  excess,  has  a  tur- 
bid instead  of  a  transparent  appearance,  this  is  an  indication  of 
the  presence  of  alkaline  sulphides.  In  this  case  it  is  best  before 
titrating  to  remove  the  sulphides  of  the  alkalis  by  means  of  a 
solution  of  lead  acetate  or  of  zinc  sulphate,  filtering  and  washing 
thoroughly. 

The  following  table,  calculated  by  Fordos  and  Gelis,  gives  the 
percentage  of  cyanide  directly: 


Iodine 
Absorbed. 

Cyanide 
%. 

Iodine 
Absorbed. 

Cyanide 
%. 

Iodine 
Absorbed. 

Cyanide 

%• 

Iodine 
Absorbed 

Cyanide 
%. 

3.896 

100 

2.922 

75 

1.948 

50 

0.974 

25 

3.857 

99 

2.883 

74 

.909 

49 

0.935 

24 

3.818 

98 

2.844 

73 

.870 

48 

0.896 

23 

3.779 

97 

2.805 

72 

.831 

47 

0.857 

22 

3.740 

96 

2.766 

71 

.792 

46 

0.818 

21 

3.701 

95 

2.727 

70 

.753 

45 

0.779 

20 

3.662 

94 

2.688 

69 

.714 

44 

0.740 

19 

3.624 

93 

2.649 

68 

.675 

43 

0.701 

18 

3.585 

•      92 

2.610 

67 

.636 

42 

0.662 

17 

3.546 

91 

2.571 

66 

.597 

41 

0.623 

16 

3.507 

90 

2.532 

65 

.558 

40 

0.584 

15 

3.468 

89 

2.493 

64 

.519 

39 

0.545 

14 

3.429 

88 

2.454 

63 

.480 

38 

0.506 

13 

3.390 

87 

2.416 

62 

.441 

37 

0.467 

12 

3.351 

86 

2.377 

61 

.402 

36 

0.428 

11 

3.312 

85 

2.338 

60 

.363 

35 

0.389 

10 

3.273 

84 

2.299 

59 

.324 

34 

0.350 

9 

3.234 

83 

2.260 

58 

.285 

33 

0.311 

8 

3.195 

82 

2.221 

57 

.246 

32 

0.272 

7 

3.156 

81 

2.182 

56 

.208 

31 

0.233 

6 

3.117 

80 

2.143 

55 

.169 

30 

0.194 

5 

3.078 

79 

2.104 

54 

.130 

29 

0.155 

4 

3.039 

78 

2.065 

53 

.091 

28 

0.116 

3 

3.000 

77 

2.026 

52 

.052 

27 

0.077 

2 

2.961 

76 

1.987 

51 

1.013 

26 

0.038 

1 

ANALYTICAL  PROPERTIES.  47 

ANALYSIS  OF  COMMERCIAL  POTASSIUM  CYANIDE. 

There  are  numerous  methods,  but  only  the  most  interesting 
and  the  best  adapted,  either  in  manufacturing  or  in  gold-mining, 
will  be  cited. 

Commercial  potassium  cyanide  quite  often  contains  impuri- 
ties, such  as  the  carbonate,  sulphate,  cyanate,  formate,  sulphide, 
ferrocyanide,  sulphocyanide,  and  sometimes  chloride  of  potassium. 
Carbonates  may  be  detected  by  dissolving  the  salt  in  water  and  add- 
ing acids,  which  will  cause  effervescence,  or  adding  lime-water, 
which  will  produce  a  turbidity. 

Cyanates  may  be  detected  in  two  ways:      ," 

(1)  By  extracting  the  salt  with  alcohol  of  84°  and  adding  con- 
centrated hydrochloric  acid   to   the   alcoholic   solution,  when  car- 
bonic acid  will  be  set  free;    or 

(2)  By   adding   ammonium   chloride   to   the   alcoholic   solution 
and  boiling  urea  is  formed,  which  may  be  separated  by  evaporating 
to   dryness   on   the  water-bath,  and   taking  up   the   residue   with 
alcohol.     When  urea  is  acted   upon  by  an  alkaline  hypobromite, 
nitrogen  is  set  free. 

Formates  may  be  detected  by  adding  several  drops  of  mercuric 
chloride  to  a  boiling  solution  of  cyanide,  when,  if  formates  are  pres- 
ent, there  will  be  produced  a  precipitate  of  calomel. 

Potassium  sulphide  may  be  detected  by  the  aid  of  lead  salts, 
which  give  a  black  precipitate.  If  the  cyanide  contains  ferro- 
cyanide, its  aqueous  solution  will  give  a  precipitate  of  Prussian 
blue  with  a  ferric  salt  (pure  cyanide  gives  a  greenish  precipitate). 

Sulphocyanide  may  be  detected  by  treating  the  solution  with 
a  slight  excess  of  HC1  and  then  with  ferric  chloride,  when  a  red 
coloration  will  be  formed. 

Chlorides  may  be  detected  by  precipitating  the  solution  with  a 
slight  excess  of  silver  nitrate,  and  then  boiling  the  precipitate  in 
nitric  acid.  If  the  precipitate  completely  dissolves,  there  are  no 
chlorides. 

Analysis  of  Cyanates.  (Method  of  0.  Hertig,  Zt.  fur  angew. 
Chem.  1901,  p.  619.) — The  method  is  based  on  the  decomposition 
of  cyanates  by  hydrochloric  or  sulphuric  acid,  with  formation  of 
an  ammoniacal  salt: 


48  THE  CHEMISTRY  OF  CYANOGEN. 

(1)  CNOK+2HC1  +  H20  =  KC1+NH4CH-C02. 

(2)  2CNOK  +  2H2S04  +  2H20  =  (NH^  2S04  4-  K2S04  +  2C02. 


Dissolve  0.2-0.5  gram  cyanide  in  a  porcelain  dish  in  several 
cubic  centimeters  of  water.  Add  either  dilute  HC1  or  H2S04  and 
evaporate  to  dryness.  Take  up  with  water.  The  solution  contains 
ammonia,  which  may  be  determined  by  boiling  with  soda,  the  ammo- 
nia being  driven  off  and  collected  in  n/5  sulphuric  acid,  which  is 
afterward  titrated,  using  fluorescein  as  indicator. 

Determination  of  Potassium.  —  If  this  is  done  by  means  of  plati- 
num chloride,  after  the  cyanates  have  been  decomposed  with 
HC1,  the  presence  of  ammonium  chloride  may  lead  to  errors.  It  is 
necessary  in  this  case,  after  the  cyanates  have  been  decomposed 
by  HC1,  to  drive  off  the  ammonia  at  a  dull  red  heat  in  a  platinum 
dish. 


BUIGNET  S  METHOD  FOR  THE  DETERMINATION  OF  HYDROCYANIC  ACID 
IN  MEDICINE,  AND  IN  DISTILLATES  FROM  BITTER  ALMONDS  OR 
LAUREL-  CHERRY. 

This  method  is  based  on  the  fact  that  when  a  solution  of  hydro- 
cyanic acid  or  an  alkaline  cyanide  containing  an  excess  of  ammonia 
is  treated  with  a  solution  of  copper  salt,  there  is  first  formed  a  double 
salt  of  copper  and  ammonium,  which  is  colorless.  When  the  reac- 
tion is  complete,  the  ammonia  acts  on  the  copper  salt  added  and 
gives  the  characteristic  blue  color.  This  indicates  the  end  of  the 
reaction,  which  takes  place  as  follows: 

4CNNH4  +  CuS04  =  (NH4)  2S04 + Cu(CN)  2,2CNNH4. 

For  this  purpose  there  is  used  a  copper-sulphate  solution  containing 
23.102  grams  of  the  pure  crystalline  salt,  free  from  efflorescence, 
per  liter  of  water.  Take  1  cc.  of  the  medicinal  hydrocyanic  acid, 
or  100  cc.  of  the  laurel-cherry  or  bitter-almond  extract,  or  0.5  gram 
of  alkaline  cyanide  dissolved  in  about  100  cc.  water,  and  to  such  a 
solution  add  10  cc.  ammonia,  and  stir.  Then  add,  drop  by  drop, 
the  solution  of  copper  sulphate,  stirring  constantly,  till  the  blue  color 
becomes  permanent.  Each  drop  of  the  copper  solution  produces 


ANALYTICAL  PROPERTIES.  49 

at  first  a  pinkish  spot,  which  later  changes  to  a  delicate  purple  when 
the  end  reaction  is  near  completion.  At  this  point  the  further 
addition  of  copper  salt  must  be  done  with  care.  This  method  is 
scarcely  applicable  except  for  cherry  water-extract.  It  gives  results 
which  are  inexact,  especially  if  a  too  large  amount  of  water  be  added; 
because  the  cuproammonium  cyanide  may  be  decomposed  by  water. 
It  happens  sometimes  that  even  in  the  titration  of  the  cherry  solu- 
tion there  is  formed,  from  the  first,  a  permanent  violet  color,  which 
interferes  with  the  delicacy  of  the  reaction,  especially  at  the  end. 
This  may  be  remedied  by  the  addition  of  carbonate  of  ammonia 
(10  cc.  of  a  solution  containing  1  part  ammonium  c  rbonate,  4  parts 
water,  and  1  part  strong  ammonia). 

FERROCYANIDES. 

Erlenmeyer's  method  is  the  one  most  generally  used  in  the  deter- 
mination of  ferrocyanide.  It  is  based  on  the  precipitation  of  ferro- 
cyanide  as  Prussian  blue.  It  is  both  rapid  and  'accurate. 

Another  method  is  based  on  the  following :  When  an  acidified 
solution  of  commercial  ferrocyanide  is  treated  with  potassium  per- 
manganate, the  potassium  ferrocyanide  alone  produces  an  oxidation 
product  capable  of  reproducing  the  raw  material  under  the  influence 
of  ferrous  oxide  in  alkaline  solution,  while  none  of  the  other  oxidized 
substances  are  at  all  affected  by  this  same  ferrous  oxide. 

The  mode  of  procedure  is  as  follows :  3  grams  of  ferrocyanide  are 
dissolved  in  water  in  a  500-cc.  graduated  flask.  The  solution  is 
acidified  with  sulphuric  acid,  and  then  a  concentrated  solution  of 
potassium  permanganate  is  added  until  a  permanent  red  coloration 
is  obtained  after  several  minutes7  shaking.  The  solution  is  allowed 
to  stand  one-half  hour.  Caustic  soda  is  then  added  in  large  excess, 
and  the  solution  brought  to  the  temperature  of  boiling  water,  with 
constant  stirring.  To  the  hot  solution  sulphate  of  iron  is  added 
till  a  black  precipitate  of  magnetic  iron  oxide  is  produced.  The 
solution  is  cooled,  made  up  to  500  cc.  with  water,  and  filtered.  In 
an  aliquot  of  the  filtrate,  acidified  with  sulphuric  acid,  ferrocyanide 
is  determined  by  titrating  with  potassium  permanganate.  This 
method  requires  about  one  hour. 

There  is  another  method,  based  on  the  insolubility  of  potassium 


50  THE  CHEMISTRY  OF  CYANOGEN. 

feirocyanide  in  dilute  alcohol,  but  it  is  applicable  only  when  the 
solution  contains  at  least  15%  ferrocyanide. 

To  70  cc.  of  95°. alcohol,  acidified  with  acetic  acid,  10  cc.  of  the 
ferrocyanide  solution  is  added.  The  ferrocyanide  is  precipitated 
as  a  crystalline  powder,  which  may  easily  be  separated  by  filtra- 
tion. After  washing  with  95°  alcohol,  the  filter  is  dried  at  100°, 
the  precipitate  redissolved  in  water  and  titrated  with  permanganate. 

SULPHOCYANIDES. 

The  solution  of  sulphocyanide  is  precipitated  with  a  standard 
solution  of  silver  nitrate,  using  a  ferric  salt  as  indicator. 

The  blood-red  color  disappears  as  soon  as  there  is  an  excess  of 
silver  solution  showing  the  end  of  the  reaction. 

Or  the  reverse  may  be  done,  and  this  latter  procedure  is  pre- 
ferable: To  a  solution  of  sulphocyanide  add  an  excess  of  standard 
silver  nitrate,  and  titrate  this  excess  with  standard  sulphocyanide. 
In  this  case  the  end  of  the  reaction  is  indicated  by  the  appearance 
of  the  permanent  red  coloration. 

DETERMINATION    OF    FERROCYANIDES    IN    THE    PURIFYING    MATERIALS 
OF   ILLUMINATING-GAS. 

Knubblauch's  Method  (1889). — This  method  consists  in  trans- 
forming insoluble  compounds  into  a  soluble  salt,  purifying  this 
product,  and  titrating  the  ferrocyanide  therein  by  means  of  a 
copper  salt. 

250  grams  substance  are  dried  at  50-60°  C.  for  6  hours.  The 
dried  mass  is  passed  through  a  sieve  (360  meshes  per  sq.  cm.).  10 
grams  of  the  sifted  material  are  transferred  to  a  graduated  255  cc. 
flask,  and  50  cc.  n/10  solution  of  potash  added.  Allow  the  solu- 
tion to  stand,  with  frequent  shaking,  for  15  hours.  Fill  the  flask 
up  to  the  255-cc.  mark  and  filter.  100  cc.  of  filtrate  are  added  to 
an  hydrochloric  acid  solution  of  ferric  chloride  (60-  grams  FeCls 
in  200  cc.  HC1  sp.  gr.  1.19,  and  solution  made  up  to  a  liter).  The 
precipitate  is  rapdily  filtered  through  a  folded  filter  and  washed 
with  hot  water.  The  filter  and  precipitate  are  transferred  to  a 
250-cc.  flask  and  treated  with  20  cc.  n/10  potash  in  order  to  con- 
vert the  Prussian  blue  into  ferrocyanide  of  potassium.  The  solu- 


ANALYTICAL  PROPERTIES.  51 

tion  is  then  made  up  to  250  cc.  and  filtered.  If  filtrate  contains 
no  hydrogen  sulphide,  it  is  acidified  and  then  titrated  with  a  standard 
copper  solution.  If  the  filtrate  contains  hydrogen  sulphide,  it  is 
advisable  to  add  1-2  grams  lead  carbonate,  shaking,  and  filtering. 
100  cc.  of  this  filtrate  (1.6  grams  original  material)  are  acidified 
with  5-6  cc.  n/5  sulphuric  acid  and  then  titrated  with  the  following 
copper  solution: 

Water 1000  cc. 

Copper  sulphate 12-13  grams, 

which  is  standardized  by  means  of  a  solution  of  potassium  ferro- 
cyanide  containing  4  grams  of  the  pure  salt  per  liter.  The  end 
of  the  reaction  is  noted  by  taking  up  a  drop  of  the  solution  and 
moistening  filter-paper  which  has  been  treated  with  ferric  chloride. 

Moldenhader  and  Leybold's  Method  (1889). — This  consists  in 
decomposing  the  ferrocyanides  by  evaporating  them  with  sulphuric 
acid,  and  determining,  by  means  of  permanganate,  the  iron  in  the 
sulphate  of  iron  remaining,  after  having  previously  converted  it 
into  the  form  of  protoxide  salt. 

Place  50  grams  of  the  finely  pulverized  substance  in  a  liter  flask 
with  100  cc.  of  an  n/10  solution  of  soda,  containing  also  2%  anhy- 
drous sodium  carbonate.  Let  the  flask  stand  in  a  warm  place  for 
4  or  5  hours,  then  make  up  the  solution  to  1030  cc.  Shake,  filter, 
and  evaporate  100  cc.  of  the  filtrate  in  a  porcelain  dish  to  10  cc. 
Transfer  these  10  cc.  to  a  platinum  dish,  add  25  cc.  n/10  solution 
of  H2S04,  being  careful  of  a  too  lively  effervescence.  Evaporate 
dry  on  a  sand-bath,  and  heat  the  dish  to  redness.  The  residue  in 
the  dish  is  a  mixture  of  ferric  sulphate  and  bisulphate  of  sodium. 
Cool,  and  dissolve  the  mixture  in  rt/10  sulphuric  acid,  washing  out 
the  dish  with  this  n/10  sulphuric  acid,  so  that  about  100  cc.  in  all 
may  be  used,  then  rinse  with  50  cc.  hot  water.  Make  up  the  solu- 
tion to  250  cc.,  add  10  grams  pure  zinc  and  1  cc.  ?i/10  copper  sul- 
phate solution.  Heat  on  water-bath  3  hours;  this  reduces  com- 
pletely the  ferric  sulphate  (test  with  potassium  sulphocyanide) . 
Cool,  filter  and  dilute  to  400  cc.,  and  titrate  with  permanganate  to 
a  slight  pink  (deduct  0.4  cc.,  due  to  the  same  quantity  of  water,  acid, 
copper,  and  zinc,  in  blank  determination).  From  the  number  of 
cubic  centimeters  of  permanganate  used,  the  amount  of  ferrocyanide 
or  of  Prussian  blue  found  in  the  spent  oxide  may  be  easily  calculated. 


52  THE  CHEMISTRY  OF  CYANOGEN. 

Burschell's  Method. — Treat  20  grams  of  the  dried  and  pulverized 
mass;  moistened  with  a  little  water,  with  200  cc.  of  a  solution  of 
potassa  (1-2).  Shake  and  let  stand  several  'hours,  then  make  up 
to  260  cc.  (10  cc.  extra  due  to  the  volume  of  the  mass),  shake  and 
filter.  Add  100  cc.  of  the  filtrate  to  a  solution  of  ferric  alum  dis- 
solved in  hot  sulphuric  acid.  Filter  the  Berlin-blue  precipitate,  wash 
with  hot  water,  and  then  transfer  paper  and  precipitate  to  a  500-cc. 
flask.  Add  a  little  water,  15  grams  mercuric  oxide,  and  1  gram 
ammonium  sulphate.  Heat  to  boiling  for  about  a  quarter  of  an 
hour,  and  after  cooling  add  1  cc.  of  a  saturated  solution  of  mer- 
curous  nitrate,  Hg2(N03)2,  and  ammonia  so  long  as  a  precipitate 
is  formed.  Make  a  solution  up  to  500  cc.,  shake  and  filter.  Transfer 
200  cc.  of  the  filtrate  to  a  400-cc.  flask,  add  6  cc.  ammonia  (sp.  gr. 
0.9)  and  7  grams  zinc  powder  (the  cyanogen  in  cyanide  of  mercury 
is  thus  transposed,  and  recombined  as  ammonium  cyanide),  shake 
for  a  few  minutes,  then  add  2  cc.  of  a  30%  solution  of  potassia  and 
make  up  to  400  cc.  Shake  and  filter. 

Allow  100  cc.  of  the  filtrate  (  =  0.875  gram  original  substance) 
to  run  into  an  excess  of  n/10  solution  silver  nitrate  (40  cc.  are  gen- 
erally enough)  contained  in  a  400-cc.  flask.  Add  dilute  nitric  acid 
and  make  up  to  400  cc.  Filter  and  titrate  200  cc.  of  the  filtrate 
with  an  n/20  solution  of  ammonium  sulphocyanide  after  first  adding 
5  cc.  of  a  saturated  solution  oi  iron  alum. 

The  end  of  the  reaction  is  indicated  by  a  clear  brown  colora- 
tion. 1  cc.  Ti/10  silver- nitrate  solution  corresponds  to  0.007042  gram: 
Fe(CN)6K4+3H20  or  to  0.003832  gram  Prussian  blue. 

Zaloziecki's  Method  (Zt.  fur  angew.  Chem.  1890,  p.  210).— 20 
grams  of  the  dry,  pulverized  purifying  material  are  transferred  to 
a  100-cc.  cylinder  with  20  cc.  of  a  10%  solution  of  potassa.  Heat 
on  water-bath  one  half -hour,  cool,  make  up  to  100  cc.;  take  45  cc., 
which  corresponds  to  10  grams  original  substance  (assuming  that 
the  20  grams  occupy  a  volume  equal  to  10  cc.),  and  heat  over  free 
flame  till  no  more  ammonia  is  set  free.  Neutralize  the  solution 
exactly  with  dilute  HC1  or  H2S04,  using  phenolphthalein  as 
indicator.  When  the  solution  is  neutralized,  add  20  cc.  normal 
potassium  carbonate  and  5  grams  moist  zinc  carbonate,  heat 
one  half-hour  while  passing  a  stream  of  carbonic  acid  through  the 
solution. 


ANALYTICAL  PROPERTIES.  53 

After  cooling,  dilute  to  100  cc.,  and  titrate  50  cc.  (  =  5  grams 
substance)  with  n/10  acid,  using  methyl  orange  as  indicator. 

By  deducting  the  amount  of  acid  equivalent  to  10  cc.  potassium 
carbonate  normal  solution  and  multiplying  the  remaining  number 
of  cubic  centimeters  by  0.46,  the  per  cent  of  potassium  ferrocyanide, 
Ee(CN)6K4+3H20,  is  obtained. 

E.  Donath  and  B.  M.  Margosche's  Method  (Zt.  fur  angew.  Chem. 
1899,  p.  345). — This  method  is  based  on  the  fact  that  the  ferro- 
cyanides  and  ferricyanides  of  the  alkalis  are  easily  decomposed,  in 
alkaline  solution,  by  oxidizing  agents. 

The  whole  of  iron  separates  as  ferric  oxide,  and  this  element 
may  be  quite  accurately  determined  in  the  precipitate,  by  known 
methods.  The  following  is  the  mode  of  procedure: 

Grind  the  purifying  material  quickly  in  an  iron  mortar.  Transfer 
50  grams  into  a  liter  flask,  add  100-150  cc.  of  a  15%  solution  of 
caustic  potash  Allow  the  flask  to  stand  in  a  warm  place  for  some 
time,  shaking  frequently.  Complete  the  volume  to  1030  cc.  and 
filter  through  a  folded  filter.  To  an  aliquot  part  of  the  filtrate  add 
a  bromated  solution  of  caustic  soda  (prepared  by  dissolving  80 
grams  of  sodium  hydrate  in  water,  cooling  and  making  up  to  1000  cc., 
and  adding  20  cc.  of  bromine,  shaking  thoroughly).  Heat  for  some 
time.  Under  these  conditions  there  is  formed  an  abundant,  thick, 
pulverulent  precipitate  of  a  beautiful  brick-red  color,  together  with 
a  lively  liberation  of  gas.  Let  the  precipitate  settle  several  hours, 
filter  and  wash.  It  may  be  dissolved  on  the  paper  with  hot  dilute 
HC1  and  the  iron  reprecipitated  with  ammonia.  But  it  is  preferable 
to  dry  the  precipitate  on  the  paper,  then  to  transfer  it  to  a  small 
flask,  to  burn  the  paper,  and  fuse  the  ash  thus  obtained  with  potas- 
sium bisulphate,  and  to  add  this  product  to  the  remainder  of  the 
precipitate  in  the  flask.  The  whole  is  then  dissolved  in  dilute  sul- 
phuric acid.  Reduce  with  zinc  and  titrate  the  iron  by  means  of 
potassium  permanganate. 

The  amount  of  iron  multiplied  by  7.5476  gives  the  quantity 
of  crystallized  salt,  K4Fe(CN)6+3H20,  or  multiplied  by  6.5833 
gives  the  amount  of  anhydrous  salt. 


54  THE  CHEMISTRY  OF  CYANOGEN. 

DETERMINATION    OF    PRUSSIAN    BLUE    IN    THE    SPENT    OXIDES. 

Method  of  Dr.  Nauss  of  the  gas-works  at  Carlsruhe. 
This  is  based  on  the  decomposition  of  Prussian  blue  by  alkalis, 
which  are  combined  as  follows: 

=  4Fe(OH)3+3Fe(CN)6Na4. 


Prussian  blue  is  treated  with  hot  caustic  soda,  the  reaction  being 
complete  when  the  green  coloration  has  disappeared. 

The  following  is  the  mode  of  procedure: 

Weigh  10  grams  of  the  material  and  place  in  a  500-  cc.  flask  con- 
taining 50  cc.  of  a  10%  solution  of  caustic  soda.  Shake  often, 
and  allow  the  flask  to  stand  at  ordinary  temperature  till  the  whole 
of  the  blue  has  been  decomposed  by  the  caustic  alkali.  This  requires 
about  15  hours.  The  formation  of  sodium  sulphide  is  avoided 
if  a  dilute  solution  of  soda  be  used.  When  the  decomposition  is 
ended  make  solution  up  to  505  cc.  with  water  (the  5  cc.  extra  are 
for  the  volume  of  iron  oxide).  Shake  thoroughly  and  filter.  Take  an 
aliquot  part  —  e.g.  50  cc.  =  1  gram  substance  —  add  10-15  cc.  of  a  hot 
acid  solution  (consisting  of  200  grams  ferric  alum,  one  liter  water, 
and  100  cc.  sulphuric  acid)  in  order  to  decompose  the  sodium  ferro- 
cyanide  contained  in  the  Prussian  blue.  Heat  on  water-bath  till 
the  pungent  odor  is  no  longer  apparent  and  filter  through  a  funnel 
surrounded  with  hot  water.  Wash  with  hot  water  till  the  filtrate 
is  free  from  sulphuric  acid.  The  residue  which  contains  all  the 
Prussian  blue  is  transferred  to  a  flask  to  which  water  is  added. 
Bring  the  solution  to  boiling,  stirring  continually.  The  quantity 
of  blue  may  then  be  determined  with  a  solution  of  sodium  hydroxide. 
It  is  necessary  in  order  to  decompose  the  whole  of  the  blue  to  add 
successively  the  required  amount  of  n/5Q  solution.  The  decom- 
position takes  place  rapidly  if  the  solution  be  heated  several  moments, 
and  the  excess  of  the  sodium  hydroxide  may  be  titrated  anew  against 
n/50  acid.  The  reaction  is  ended  when  the  green  coloration  is  per- 
manent. 

TOXICOLOGICAL    RESEARCH. 

Substances  in  which  the  existence  of  cyanogen  compounds  is 
suspected  are  finely  divided  and  diluted  with  distilled  water  so 
as  to  form  a  light  pulpy  mass.  This  is  acidified  with  tartaric  or 


ANALYTICAL  PROPERTIES.  55 

phosphoric  acid  (acids  which  have  no  action  on  hydrocyanic  acid, 
but  capable  of  setting  it  free  from  cyanides).  This  mixture  is 
placed  in  a  tubular  retort  provided  with  a  straight  safety-tube 
and  connected  with  a  bent  tube  which  plunges  to  the  bottom  of 
a  double  tubular  Woolf  bottle.  This  latter  is  connected  with  a 
bulb-tube.  Both  of  these  contain  a  dilute  solution  of  silver  nitrate. 
Heat  gently  on  the  water-bath  so  as  to  produce  a  slow  ebullition,  which 
must  be  carefully  watched.  Under  these  conditions  the  presence 
of  hydrocyanic  acid  is  shown  by  the  formation  of  a  white  precipi- 
tate of  silver  cyanide  in  the  Woolf  bottle  and  in  the  bulb-tube. 
When  the  precipitate  no  longer  increases  the  distillation  is  stopped. 
Cool  and  unite  the  solutions  of  the  bulb-tube  and  the  bottle;  filter, 
wash,  dry  at  100°  C.,  and  weigh. 

But  as  quite  often  substances  to  be  analyzed  contain  hydro- 
chloric acid,  which  would  give  a  perfectly  analogous  precipitate, 
it  is  well  to  make  sure,  by  means  of  the  ordinary  reactions  which 
we  have  already  described,  that  one  has  really  to  do  with  cyanogen 
or  its  compounds. 

Moreover,  it  is  to  be  noted  that  cyanide  of  mercury  gives  neither 
the  reactions  of  mercury  nor  those  of  the  cyanides.  One  may 
either  precipitate  the  mercury  with  hydrogen  sulphide,  filter,  and 
test  for  hydrocyanic  acid,  as  indicated  above,  or  else,  and  this  is 
preferable,  plunge  blades  of  iron  for  a  sufficient  length  of  time  into 
the  extracted  solutions  of  the  substances  suspected,  which  have 
been  acidified  with  sulphuric  acid.  The  mercury  is  precipitated 
by  the  hydrogen  and  the  cyanogen  converted  into  hydrocyanic 
acid. 


CHAPTER  IV. 

THERMOCHEMICAL    DATA    RELATING    TO    THE    CYANIDE 

COMPOUNDS. 

IN  order  to  complete  this  general  study  it  seems  necessary  to 
give  some  thermochemical  information  relative  to  the  •  principal 
cyanated  compounds. 

The  following  outline  is  taken  from  Berthelot's  remarkable 
work  Sur  la  force  des  matieres  explosives,  d'apres  la  thermo- 
chemie  (t.  II.,  p.  64,  etc.): 

I.    CYANOGEN. 

The  heat  of  formation  of  cyanogen  determined  by  Berthelot 
by  ordinary  combustion  or  by  detonation  is 

C4  (diamond)  +  N2  =  C4N2-74.5  cal.1 

From  this  number  Berthelot  draws  the  following  conclusions: 
"  Cyanogen  (C2N),  as  well  as  acetylene  (C2H)  and  nitrogen  dioxide 
(N02)  and  all  substances  which  play  the  role  of  true  compound 
radicals,  is  a  body  whose  formation  is  accompanied  by  the  absorp- 
tion of  heat,  a  circumstance  which  seems  to  be  of  such  a  nature  as 
to  explain  the  very  character  of  this  real  compound  radical,  mani- 
festing in  its  combinations  a  greater  energy  than  in  its  free  elements. 
The  energy  of  these  latter  becomes  stronger  rather  than  weaker 
because  of  this  absorption  of  heat,  as  is  the  case  in  combinations 
which  give  off  heat,  and  this  increase  of  energy  renders  the  com- 
pound system  comparable  to  the  most  active  elements." 

xThe  same  notation  is  used  in  this  chapter  as  that  used  in  Berthelot's  work. 

56 


THERMOCHEMICAL  DATA.  57 


II.    HYDROCYANIC   ACID. 

The  heat  of  formation  of  hydrocyanic  acid,  determined  by  vari- 
ous methods  by  Berthelot,  may  be  expressed  thus: 

C2  (diamond)  +N  +  H  =  C2NH  (gaseous)    = -29.5  cal. 
=  C2NH  (liquid)       =  -23.8  "' 
=  C2NH  (dissolved)  =-23.8  ff 

"  It  follows  from  these  figures/'  says  Berthelot,  "  that  hydro- 
cyanic acid  is  formed  from  its  elements  with  absorption  of  heat, 
which  explains  the  readiness  with  which  this  acid  forms  direct 
combinations,  polymeric  compounds,  and  brings  about  complex 
reactions." 

Berthelot  remarks  further  that  "  cyanogen  and  hydrocyanic 
acid,  acetylene,  etc.,  could  be  regarded  as  formed  with  liberation  of 
heat,  if  it  were  admitted  that  carbon,  when  considered  as  diamond 
or  charcoal,  does  not  correspond  to  the  real  elementary  carbon, 
which  should  be  comparable  to  hydrogen  and  probably  gaseous, 
while  the  diamond  and  charcoal  represent  its  allotropic  modifica- 
tions. In  passing  from  its  gaseous  to  its  polymeric  and  condensed 
state,  elementary  carbon  would  liberate  a  considerable  quantity 
of  heat,  and  greater  than  the  heat  absorbed  in  the  formations  of 
acetylene  (-30.5  cal.  for  C2  =  12),  and  of  cyanogen  (-37.3  cal.)" 

The  actual  figures  show  that  the  formation  of  hydrocyanic  gas 
starting  with  cyanogen  and  hydrogen  is 

Cy  +  H  =  CyH        liberates  +  7.8  cal. 

"  This  formation  is  therefore  exothermic,"  a  circumstance  which 
led  Berthelot  to  foresee  that  it  could  be  brought  about  directly; 
and,  in  fact,  the  illustrious  savant  did  succeed,  contrary  to  the 
negative  experiments  previously  worked  out  by  Gay-Lussac,  in 
combining  the  two  gases  directly  under  the  influence  only  of  time 
and  heat.  The  synthesis  of  hydrocyanic  acid  by  means  of  acetylene 
and  nitrogen,  both  in  the  free  state,  by  the  electric  spark,  which 
was  discovered  by  Berthelot  in  1868,  liberates  +2.1  cal. 


58  THE  CHEMISTRY  OF  CYANOGEN. 


III.     CYANIDE    OF   POTASSIUM. 

The  heat  liberated  by  the  formation,  from  its  elements,  of  solid 
•cyanide  of  potassium,  determined  by  Berthelot,  is  as  follows" 

C2  +  N  +  K  =  C2NK  crystallized  liberates  +  30.3  cal. 

The  direct  formation  of  potassium  cyanide,  by  means  of  the 
union  of  its  elements,  in  the  same  proportion  by  weight  as  repre- 
sented by  the  equation,  cannot  be  brought  about,  in  fact,  at  the 
ordinary  temperature.  But  it  is  admitted  that  it  does  take  place 
at  a  very  high  temperature,  if  free  nitrogen  is  made  to  act  upon 
charcoal  impregnated  with  potassium  carbonate,  that  is,  under 
the  conditions  where  nascent  potassium  is  formed. 

"  At  this  temperature  cyanide  of  potassium  is  a  liquid,  per- 
haps even  gaseous,  change  of  state  which  absorbs  heat,  but  on  the 
other  hand  the  potassium  is  gaseous,  which  fact  somewhat  com- 
pensates. If  the  free  nitrogen,  carbon,  and  potassium  really  do 
combine,  without  other  intermediary  reaction,  as,  e.g.,  the  formation 
of  an  acetylide  (which  has  not  been  proved),  one  will  have  to  admit 
that  the  total  synthesis  of  cyanide  of  potassium  liberates  heat  under 
the  real  conditions  in  which  it  is  effected. 

"  Whether  the  liberation  is  produced  all  at  once  or  only  by 
successive  reactions,  it  explains  the  total  synthesis  no  less. 

"  The  union  of  cyanogen  with  potassium  takes  place,  as  is  known 
directly.  This  union  calculated  for  the  following  states: 

Cy  (gas)  +K  (solid)  =  KCy  (crystallized)        liberates  +  67.6  cal. 

"  This  figure  justifies  the  direct  synthesis  of  cyanide  of  potassium 
by  means  of  cyanogen,  but  the  heat  liberated  is  less  than  that  liberated 
in  the  union  of  the  same  metal  with  the  gaseous  halogen  elements." 

The  latter  is 

C1+K  =  KC1  =  4-105.6  cal. 
Br  gas  +  K  =  KBr  =  +  100.4  rf 
I  solid  +  K  =  KI    =  +  85.4  <r 
=  KCy=+  67.6  " 


Berthelot  attributes  to  this  inferiority  in  the  amount  of   heat 
liberated  the  decomposition  of  solutions  of   potassium  cyanide  by 


THERMOCHEMICAL  DATA.  59 

the  halogens,  and  further  says  that  "  the  cyanogen  which  should 
be  set  free  is  combined  moreover  with  one  half  of  the  halogen  body, 
not  without  a  slight  liberation  of  additional  heat  (  +  1.6  cal.  for 
€yCl  gas,  +4.2  cal.  for  Cyl  solid).  Then  he  compares  the  quan- 
tities of  heat  liberated  when  starting  with  the  hydracids  and  dilute 


€yH  (dilute)  +  KO  -  OH  (dilute)  =  KCy     dissolved  +  H202  =  +  3.0  cal., 

which  is  a  quantity  much  less  than  that  liberated  in  the  formation 
of  the  chloride,  bromide,  or  iodide  of  potassium  (  +  13.7  cal.).  With 
gaseous  hydracids  the  disagreement  is  still  greater  (  +  17  cal.). 
Berthelot  concludes  from  this  that  "  hydrocyanic  acid  is  a  much 
weaker  acid  than  the  hydracids  derived  from  the  halogen  elements, 
and  that  it  is  even  displaced  in  potassium  cyanide  dissolved  by 
most  of  the  acids. 

"  The  transformation  of  potassium  cyanide  into  potassium 
formate : 

C2NK  (dissolved) +2H202  =  C2HK04  dissolved  +  NH3  dissolved, 
liberates +9. 5  cal. 

"  That  is  the  reaction  which  goes  on  slowly  in  solutions  of  potas- 
sium cyanide. 

"  The  same  reaction  carried  on  on  the  dry  salt  by  water- vapor 
produces  formate,  and  also  ammonia  gas.  It  is  much  more  rapid, 
but  it  also  liberates  twice  the  amount  of  heat,  +17.7  cal.  If  the 
temperature  is  raised,  this  reaction  becomes  complicated  because 
of  the  subsequent  destruction  of  the  formate  by  heat  or  by  an  excess 
of  alkali,  a  reaction  which  takes  place  at  about  300°  and  which 
transforms  completely  potassium  cyanide  into  potassium  carbonate: 
C2NK  solid  +  KO-  OH  solid +  2H202  gaseous 

=  C204+2KO    solid  +NH3  gas     -    liberates  +37.4  cal. 

"  I  call  attention  to  this  because  it  is  one  of  the  most  active 
causes  of  the  destruction  of  potassium  cyanide  during  its  manu- 
facture, where  one  works  with  the  fused  salts,  a  fact  which  slightly 
modifies  the  figures  above,  without  modifying  the  general  signifi- 
cance of  them." 


60  THE  CHEMISTRY  OF  CYANOGEN. 


IV.     CYANHYDRATE   OF  AMMONIA. 

The  formation  of  solid  ammonium  cyanide  starting  with  gaseous 
hydrocyanic  acid  and  gaseous  ammonia  liberates  +20.5  cal.;  and 
starting  with  the  elements +40. 5  cal. 


V.    FERROCYANIDE   OF  POTASSIUM. 

Because  of  the  difficulty  in  obtaining  pure  hydroferrocyanic 
acid  Berthelot  determined  the  heat  of  formation  of  this  acid 
in  an  indirect  way,  i.e.,  by  displacing  it  from  its  salts  by  a  more 
energetic  acid. 

"  By  mixing  a  dilute  solution  of  potassium  ferrocyanide,  CysFeK^ 
=  4  liters,  with  dilute  hydrochloric  acid  (1  equiv.  =  2  liters),  no 
change  of  temperature  is  observed;  either  there  is  no  reaction,  or 
the  two  acids  liberate  the  same  quantity  of  heat  in  combining  with 
the  potassa,  in  which  case  the  base  in  the  solution  could  be  divided. 
The  latter  case  is  the  more  likely.  In  fact,  by  mixing  ferrocyanide 
with  dilute  sulphuric  acid  a  progressive  separation  and  a  displace- 
ment which  tends  to  become  complete,  in  the  presence  of  a  large 
excess  of  sulphuric  acid,  are  observed.  Thus 

Cy3FeK2  (6  liters) +HS04  (1  equiv.  =  2  liters)  liberates  +1.107  cal. 
Cy3FeK2  (6  liters) +2HS04  (1  equiv.  =  2  liters)  liberates  +0.181  cal. 

By  continuing  the  gradual  addition  of  sulphuric  acid  an  absorption 
of  heat  is  produced,  due  to  the  formation  of  bisulphate. 
"With  a  large  excess  added  all  at  one  time 

Cy3FeK2  (4  liters)  +10HS04  (1  equiv.  =  2  liters)  liberates  +0.966  caL 

"  These  phenomena  are  comparable  to  the  reaction  of  sulphuric 
acid  on  the  chlorides,  although  the  results  are  somewhat  different. 
Here  likewise  is  a  progressive  division  of  the  base  between  the  two 
acids.  If  it  be  admitted  that  the  10HS04  be  sufficient  to  remove 
almost  the  whole  of  the  potassa  from  the  ferrocyanide,  similar  to 
that  which  is  produced  with  the  chlorides,  nitrates,  etc.,  the  heat 
x  liberated  in  the  reaction  of  dissolved  hydroferrocyanic  acid  on 


THERMOCHEMICAL  DATA.  61 

dilute  potassa  may  be  calculated.  In  fact,  +15.7  cal.  being  the 
heat  liberated  in  the  reaction  of  sulphuric  acid  on  potassa,  and 
-1.75  cal.  the  heat  absorbed  in  the  reaction  of  dilute  4HS04  on 
dissolved  potassium  sulphate  (formation  of  bisulphate),  the  desired 
reaction  will  be 

4(Cy3FeH2=4  liters) +KO(1  equiv.  =  2  liters)  liberates 
x  =  + 15.71  - 1.75  -4(0.97)  =  + 13.5  cal. 

"  This  figure  is  practically  the  same  as  that  which  represents, 
the  heat  liberated  by  hydrochloric  acid  and  nitric  acid  when  acting 
on  potassa,  from  which  it  follows  that  hydroferrocyanic  acid  is  a 
strong  acid  comparable  to  the  mineral  acids.  It  is  known  that 
it  displaces  carbonic  and  acetic  acids.  The  absence  of  apparent 
thermic  reaction  between  HC1  and  dissolved  cyanoferride  is  in 
harmony  with  these  results. 

"  Nothing  is  easier  than  passing  through  that  to  the  formation 
of  Prussian  blue;  in  fact 

i(Cy3FeK2=4  lit.)+S04Fe(l  eq.  =  2  lit.)  =  -JCy3Fefe  precipitated 
+  KS04  dissolved        liberates +2. 54  to  2.78  cal., 

the  amount  of  heat  liberated  increasing  with  length  of  time,  as  often 
happens  in  the  formation  of  amorphous  precipitates.  Likewise 

| (Cy3FeK2 = 4  lit.)  +  N06fe(l    eq.  =  2    lit.)  =iCy3Fefe2    precipitated 
+ KN06  dissolved        liberates + 0.725  cal. 

"  From  the  results  obtained  with  ferric  sulphate,  the  substitu- 
tion of  potassa  for  iron  peroxide  (KO  for  FeO)  in  Prussian  blue  liber- 
ates+7. 2  cal.;  from  the  results  obtained  with  the  nitrate,  +7.2  cal., 
a  perfect  agreement. 

"  By  admitting  that  the  formation  of  cyanoferride  of  potassium, 
CyFeH2  (dilute) +2KO  dilute,  liberates +  13.5x2  =  27.0  cal.,  it  is 
thereby  concluded  that  the  formation  of  Prussian  blue  with  the 
same  acid  and  precipitated  peroxide  of  iron, 

Cy3FeH2  +  2f eO  (precipitated)        liberates  + 6.3  X  2  =  126  cal. 


62  THE  CHEMISTRY  OF  CYANOGEN. 

"  The  value  6.3  differs  but  little  from  5.7,  which  represents  the 
union  of  nitric  and  hydrochloric  acids  with  iron  peroxide,  which 
fact  is  a  new  proof  of  the  analogy  between  hydroferrocyanic  acid 
and  the  mineral  acids.  Nevertheless  +6.3  is  greater  than  +5.7, 
which  fact  explains  why  dilute  hydrochloric  acid  does  not  decom- 
pose Prussian  blue  with  formation  of  iron  chloride. 

"  Hydrocyanic  acid,  one  of  the  weakest  acids  known,  has  formed 
therefore,  by  its  association  with  iron  cyanide,  a  powerful  acid, 
comparable  in  all  points  to  hydrochloric  and  nitric  acids. 

"  This  is  a  new  proof  calculated  to  establish  the  fact  that  the 
best  characterized  acid  properties,  even  in  the  hydrocarbon  com- 
pounds, are  not  necessarily  connected  with  the  presence  of  oxygen. 

"  The  heat  liberated  in  the  formation  of  cyanoferride  itself 
remains  to  be  determined. 

"I  found  the  following  results:  S04Fe(l  eq.  =  2  lit.) +280^6 
(1  eq.  =  2  lit.)+6KO(l  eq.  =  2  lit.)  liberates  23.2  cal.  By  adding 
to  the  above  mixture  3CyH(l  eq.  =  4  lit.)  a  further  liberation  of 
+  39.3  cal.  is  observed,  which  represents  the  formation  of  cyano- 
ferride, starting  with  CNH  and  the  two  oxides: 

3CyH  (dissolved) +2KO  (dissolved)  +  FeO  (precipitated) 
=  Cy3FeK2  (dissolved)        liberates  39.3  cal. 

"  As  a  control  experiment,  I  added  to  the  solution  3HC1 
(1  eq.  =  2.  lit.),  which  liberated +25.0  cal.,  with  the  formation  of  an 
abundant  precipitate  of  Prussian  blue,  the  heat  liberated  varying 
during  the  precipitation  from  23.0  to  25.0  cal. 

"  In  short,  HC1  has  produced  the  following  reactions: 

HC1  dilute  +KO  dilute  =  KC1  dilute +  13.6  cal. 
2HC1     f(     +feOppt.    =2feCl    "     +11.4  "! 
2f eCl     ' ''     +  Cy3f eK2  dissolved  = 

Cy3Fef e2  +2KC1  dilute  +  1.4  "' 


26.4  cal. 

"  The  agreement  between  25.0  and  26.4  is  as  close  as  one  may 
expect  when  working  with  similar  precipitates,  the  state  of  which 
varies  with  the  conditions. 


THERMOCHEMICAL  DATA.  63 

"  From  that  I  conclude 

SCyH  dilute  +  FeO  ppt .  +  2f eO  ppt .  =  Cy3Fef e2  ppt .  liberates + 24.9  cal. 
3CyH  dilute  +  FeO  ppt.  =  Cy3FeH2  dissolved +  12.3  cal. 

"  I  verified  these  values  by  forming  Prussian  blue  directly  by 
means  of  CNH  and  the  two  sulphates: 

3CyH(l  eq.  =  2  lit.) +S04Fe(l  eq.  =  2  lit.) +80*16(1  eq.  =  2  lit.) 
=  Cy3Fef  e2  ppt.  +  3HS04(dilute)        liberates  +  37.5  cal. 

"  The  difference  between  the  heat  of  formation  of  alkali  sul- 
phate and  that  of  iron  sulphate  starting  from  the  oxides  being 

12.5  +  11.1-47.1=  -23.5  cal., 

and  the  heat  of  formation  of  3CyK  starting  from  potassa  being 
+8.9  cal.,  from  these  data  the  heat  liberated  in  the  formation  of 
Prussian  blue  from  CNH  is  easily  found: 

3CyH    dilute + FeO +2feO  =  Cy3Fefe2 
liberates   +37.5  +  8.9-23.2= +23.2  cal., 

a  result  which  shows  sufficient  agreement  with  +24.9  cal.,  obtained 
in  another  way,  but  which  I  regard  as  a  little  less  exact. 

"  Let  us  draw  some  general  conclusions  from  these  results.  The 
first  conclusion  is  in  regard  to  the  heat  liberated  in  the  formation 
of  cyanoferride,  starting  with  hydrocyanic  acid  or  with  potassium 
cyanide : 

SCyH  (dissolved)  +3KO  dilute  liberates +8.7  cal. 

SCyH  (dissolved)  +2KO  +  FeO  ppt.        liberates +39. 3  cal. 

"  The  substitution  of  ferrous  oxide  for  potassa  with  formation 
of  cyanoferride  liberates  a  large  amount  of  heat,  i.e., +39.3— 8.7 
=  +30.6  cal.  One  single  equivalent  of  ferrous  oxide  contributes, 
moreover,  to  the  formation  of  hydroferrocyanic  acid. 

1  This  .figure  explains,  besides,  the  observed  displacement^  and 
it  corresponds  to  the  constitution  of  a  new  molecular  type,  that 
of  hydroferrocyanic  acid. 

"  In  fact,  we  conclude  from  that 


64  THE  CHEMISTRY  OF  CYANOGEN. 

3CyH  (dissolved)  +FeO  ppt.  liberates  + 12.3  cal.,  a  quantity 
greater  than  the  heat  (+9.0  cal.)  liberated  by  3KO  (dilute)  united 
with  3CyH. 

"  That  is  because  here  there  are  two  simultaneous  reactions:  the 
union  of  3  mol.  of  CNH  into  a  type  thrice  as  much  condensed,  and 
the  combination  of  ferrous  oxide  which  enters  the  constitution  of 
this  new  type  Cy3FeH2. 

",  Likewise,  in  the  case  of  Prussian  blue,  it  has  elsewhere  been 
established  that  Cy3FeH2  (dilute)  +2feO  ppt.  liberates  + 12.6  cal. 
=  6.3X2,  i.e.,  practically  the  same  number  as  the  union  of  the  same 
oxide  with  dilute  HC1  and  HN03. 

"  Starting  from  CNH  itself  we  have 

3CyH  (dilute)  +FeO+2feO  =  Cy3Fefe2  ppt. +24.9  cal.  =  8.3X3. 

"  The  magnitude  of  this  last  figure,  which  is  three  times  the 
heat  liberated  when  potassa  unites  with  hydrocyanic  acid,  is  the 
explanation,  as  above,  of  the  formation  of  the  new  molecular  type 
of  cyanoferrides,  and  still  more  so  of  the  formation  of  the  double 
cyanides. 

"  This  superposition  of  effects  explains,  moreover,  the  superiority 
of  apparent  affinities  which  the  oxide  of  iron  shows  over  potassa 
in  its  union  with  hydrocyanic  acid,  which  is  shown  by  a  greater 
liberation  of  heat  than  in  the  formation  of  ordinary  oxysalts,  sul- 
phates, nitrates,  acetates,  etc.,  starting  with  the  dilute  acids  and 
alkaline  bases  corresponding  to  the  metallic  oxides. 

"  Would  it  not  be  possible  to  find  some  analogous  circumstance 
to  explain  how  the  oxides  of  silver  and  of  mercury,  besides  the 
oxides  of  iron,  liberate  more  heat  than  does  dilute  potassa  in  uniting 
with  hydrocyanic  acid?  That  is,  are  the  cyanides  of  silver  and 
of  mercury  really  represented  by  the  simple  formulas  CyAg,  CyHg, 
salts  comparable  to  those  of  CyK  and  CyH,  or  else  would  it  not 
be  better  to  regard  them  as  a  more  condensed  type  of  cyanides, 
such  as 

Cy2Hg2    and    Cy2Ag2? 
"  The  heat  liberated  by  their  union  with  cyanide  of  potassium 


THERMOCHEMICAL  DATA.  65 

in  the  formation  of  double  cyanides,  even  in  the  state  of  dilute  solu- 
tions, such  as 

Cy2HgK,  Cy2AgK  (rough  formulas), 

would  support  this  supposition,  for  it  would  be  the  result  of  the 
passage  from  the  simple  type,  cyanide  of  potassium,  to  the  com- 
plex type  which  constitutes  the  double  cyanides, 

Cy  2Hg2 + 2KCy  =  2Cy2HgK ; 
Cy2Ag2 + 2KCy  =  2Cy2  AgK 

"  Besides,  hydrocyanic  acid  is  not  the  only  acid  which  is  the 
occasion  of  a  general  overthrowing  of  the  ordinary  affinities,  inter- 
preted by  the  corresponding  thermic  effects  between  the  alkaline 
oxides  and  the  metallic  oxides.  Hydrogen  sulphide  is  in  exactly 
the  same  case. 

"  Notwithstanding  these  latter  considerations  it  remains  no 
less  a  fact  that  the  metallic  oxides  liberate  more  heat  than  the  alka- 
line bases,  uniting  with  hydrocyanic  acid,  a  fact  which  explains 
why  they  displace  them.  Thermochemistry  thus  takes  into  account 
the  constitution  of  the  complex  cyanides,  new  molecular  types, 
which  are  very  superior  to  the  primitive  type  because  of  the  energy 
of  their  affinities  in  regard  to  the  bases,  as  well  as  because  of  the 
stability  of  the  resultant  salts — I  mean  very  superior  to  hydrocyanic 
acid,  which  contributes  to  their  formation  by  condensation. 

"  Hydrocyanic  acid,  common  generant  of  condensed  types,  is 
distinguished,  moreover,  because  it  is  formed  from  the  elements 
with  an  absorption  of  heat — 29.5  cal.;  in  other  words,  its  formation 
has  stored  up  an  excess  of  energy  which  makes  it  specially  fit  for 
successive  combinations  and  molecular  condensations. 

"  Let  us  give,  finally,  the  heat  of  formation  of  potassium  ferro- 
cyanide  from  its  elements: 

Fe+K2+Cy3  =  Cy3FeK2  (solid)  liberates  + 183.6  cal.  or  61.2x3. 
From  simple  bodies: 

Fe+2K+3C+3N  =  C3N3FeK2+71.7  cal.  or  23.9X3. 

These  results  are  close  to  those  which  are  obtained  in  the  forma- 
tion of  potassium  cyanide,  starting  with  cyanogen +67.6  cal.,  and 
with  the  elements  +30.3  cal. 


66  THE  CHEMISTRY  OF  CYANOGEN. 

"  The  hydrated  salt  encloses  3  molecules  of  H20(3HO),  extra, 
whose  union  in  the  liquid  form  with  the  anhydrous  salt  liberated 
+  2.48  caL,  which  brings  the  total  amount  of  heat  liberated  in  the 
formation  of  the  crystalline  yellow  prussiate  from  the  elements  and 
H20,  +94.2  cal." 

VI.    POTASSIUM    CYANATE. 

The  formation  of  solid  potassium  cyanate  from  the  elements  is 
C2  diamond  +  N  +  K  +  02  =  C2NK02  liberates  + 102.0  cal. 

The  dissolved  salt  liberates  +  96.8  cal. 

The  same  formation  starting  with  dilute  KOH: 

C2  +  N + OKO  dilute  =  C2NK02  (dissolved)     liberates  + 15.5  caL 

From  gaseous  Cy: 

Cy  +  K  +  02  =  CyK02  solid  + 139 . 3  cal. 

Cy  +  0  +  KO  dilute  =  CyK02  dissolved  +51.8    rr 

Cy2+2KO  dilute  =  CyK04  dilute  +  CyK  dilute  +  34.2    "' 

All  these  results  are  greater  than  the  heat  liberated  in  the  analo- 
gous reactions  of  the  real  halogen  elements,  e.g., 

C12  gas  +  2KO  dilute  =  C102K  +  KC1  dissolved  liberates  only  +  25.4  caL 

There  is,  moreover,  this  difference,  that  the  complex  nature  of 
Cy  and  its  tendency  either  to  form  polymeric  and  other  condensed 
bodies,  or  to  regenerate  ammonia  and  its  derivatives,  are  the  cause 
of  a  number  of  secondary  reactions,  such  as  do  not  occur  in  the 
case  of  chlorine.  These  reactions  are  easier  in  proportion  as  the 
heat  liberated  by  the  direct  reaction  is  greater  and  in  proportion 
as  it  furnishes  from  that  time  a  greater  reserve  of  energy  by  other 
transformations. 

"  The  union  of  dry  potassium  cyanide  with  gaseous  oxygen  in 
the  formation  of  solid  cyanate  C2NK  (solid)  +  02  (gas)  =  C2N02K 
(solid)  would  liberate  +102.0-30.3= +71.7  cal.,  a  large  figure, 
and  about  three  fourths  of  the  heat  (+94.0)  liberated  by  the  com- 
bustion of  the  carbon  contained  in  the  cyanide. 

"  This  figure  refers  to  bodies  taken  in  their  actual  state,  a  fact 
in  which,  up  till  now,  no  absorption  of  oxygen  by  the  cyanide  of 


THERMOCHEMICAL  DATA.  67 

potassium  has  been  observed,  probably  because  it  has  not  been 
investigated.  In  the  fused  state,  on  the  other  hand,  it  easily  takes 
place,  as  is  known.  Now  these  figures  just  calculated  may  be 
approximately  applied  to  the  same  bodies,  under  the  known  con- 
ditions of  their  real  reaction,  at  a  high  temperature,  for  the  fusion 
of  the  cyanide  as  well  as  of  the  cyanate  should  absorb  about  equal 
quantities  of  heat. 

"  Considering  the  heat  liberated  by  the  oxidation  of  its  potassium 
compound,  cyanogen  agrees  more  with  iodine,  and  differs,  on  the 
contrary,  with  chlorine.  We  have  in  fact: 

KC1  +  02  =  KC104  (solid)  absorbs  -ll.Ocal., 

KBr  +  04  =  KBr04     "  "        -11.1   " 

KI    +  04  =  KI04        "  liberates  +  44.1   rr 

=  KCy02     "'  "       +71.7  « 


a  progression  inverse  to  that  which  characterizes  the  union  of  a 
like  metal,  such  as  K,  with  the  same  series  of  halogen  bodies,  such 
as  Cl  (  +  105.0  caL),  gaseous  Br  (  +  100.4  cal.),  gaseous  I  (+85.4  cal.), 
and  cyanogen  (+67.  6  cal.) 

"  From  the  preceding  figures  is  explained  why  cyanide  of  potas- 
sium has  such  a  great  tendency  to  oxidation,  either  under  the  influ- 
ence of  oxidizing  agents,  or  even  n  air. 

"  The  combustible  character  of  one  of  the  elements  of  cyanogen 
opposes,  moreover,  the  formation  of  peroxidized  acids,  as  with 
chlorine,  and  the  halogen  elements  such  compounds  would  have  too 
great  a  tendency  to  being  converted  into  carbonic  acid. 

"  The  complete  combustion  of  solid  potassium  cyanate, 

C2NK02  +  03  =  CO  K+C02  +  N,  would  liberate  +83.9  cal. 

"The  facility  with  which  potassium  cyanate  becomes  regenerated 
from  ammonia,  even  from  the  one  fact  of  its  long  contact  with 
water,  is  easily  explained  : 

C2NK02  +  2H202 

=  C03K  (dissolved)  +C02NH3HO  dissolved  liberates  +20.0  cal. 

"That  is  also  an  amide  reaction. 

"The  well-known  transformation  of  fused  cyanate  of  potassium 


68  THE  CHEMISTRY  OF  CYANOGEN. 

by  means  of  water-vapor  into  fused  carbonate  of  potassium,  car- 
bonic acid,  and  ammonia  liberates  about  +9  cal. 

"'The  conversion  of  potassium  cyanide  into  carbonate  and  am- 
monia under  the  combined  influence  of  oxygen  and  water-vapor 
at  a  high  temperature,  a  conversion  so  pernicious  in  the  industrial 
preparation  of  prussiates,  is  no  less  easily  explained  by  thermo- 
chemistry. In  fact,  at  the  ordinary  temperature  we  should  have 

C2NK  solid   +02+3HO  gaseous 

=  C03K  solid   +C02  gas   +NH3  gas   +79.3  cal. 

At  about  red   heat    this   figure    should  remain  likewise  large,  the 
cyanide  and  the  carbonate  being  partially  fused." 

For  the  thermochemical  data  referring  to  cyanogen  and  its  com- 
pounds see  the  tables  at  end  of  the  book. 


PART  TWO. 

THE  PRESENT  CONDITION  OF  THE  CYANIDE 

INDUSTRY. 


CHAPTER  V. 
COMMERCIAL  AND  INDUSTRIAL  STUDY. 

THE  development  of  the  industry  of  the  cyanated  compounds 
is  due,  as  was  stated  in  the  Introduction,  primarily  to  the  use  of 
potassium  cyanide  in  the  treatment  of  auriferous  minerals. 

At  first  the  production  of  cyanides  was,  so  to  speak,  insignificant, 
or  at  least  limited.  The  industry  was  created  in  1710  with  the  dis- 
covery of  Prussian  blue,  by  the  dyer  Diesbach,  and  for  a  long  time 
was  limited  to  this  c  mpound  used  in  dyeing.  The  discovery  of 
potassium  ferrocyanide  and  the  other  cyanogen  compounds  came, 
but  later,  and  among  these  the  ferrocyanide  alone  was  applied  in 
the  arts  and  manufactures.  Cyanide  of  potassium  did  indeed  have 
for  a  time  a  certain  limited  market  in  photography,  but  its  poisonous 
properties  and  its  relatively  high  price  made  it  give  place  to  hypo- 
sulphite of  sodium.  From  that  time  it  was  a  laboratory  and  phar- 
maceutical rather  than  an  industrial  product.  But  as  a  result  of  the 
remarkable  researches  of  MacArthur  and  Forest,  some  fifteen  years 
ago,  in  the  extraction  of  gold  by  means  of  potassium  cyanide,  this 
salt  became  industrially  important,  giving  to  the  whole  industry 
of  the  cyanide  compounds  an  impetus  and  a  vitality  which  made 
it  acquire  rapidly  its  present  development,  which  is  still  bound  to 
increase. 


70       THE  PRESENT  CONDITION  OF  THE  CYANIDE  INDUSTRY. 

The  application  of  these  methods  brought  about  as  an  immediate: 
consequence  a  considerable  increase  in  the  consumption  of  cyanide 
of  potassium  to  such  an  extent  that  in  1898  this  consumption  arose 
to  3300  tons,  and  in  the  month  of  August  of  that  year  the  demand 
was  S3  great  that  the  German  manufactories  which  produce  the 
major  part  of  this  product  were  unable  to  fill  their  orders  punctually, 
notwithstanding  the  price  had  been  advanced  29%  to  the  English 
buyers. 

In  June  1899  the  national  bureau  of  foreign  commerce  was  in 
possession  of  data  from  Johannesburg  showing  a  consumption  of 
450,000  English  pounds  of  cyanide  per  month,  which  amount  repre- 
sented a  value  of  $135,000,  delivered. 

It  is  quite  probable  that  these  figures  would  still  have  increased  had 
it  not  been  for  the  war  in  South  Africa,  and  the  consumption  in  that 
country  alone  would  have  arisen  to  10,000  tons. 

The  result  of .  this  development  is  easy  to  foresee.  The  work 
was  undertaken  most  zealously;  the  manufacturers  in  England 
and  in  Germany  especially  sought  means  of  producing  the  cyanide 
in  sufficient  quantities  to  supply  the  demand,  and  under  the  most' 
economical  conditions,  as  shall  be  seen  when  the  study  of  the  various 
meth  ds  is  taken  up.  An  active  s  ruggle  was  established  among 
the  manufacturers  of  cyanide,  the  result  of  which  has  been  infinite 
progress  in  this  industry.  Even  at  the  present  time  numerous 
researches  are  being  undertaken  along  these  lines,  and  it  is  to  be 
hoped  that  these  efforts  will  not  be  fruitless,  but  rather  a  process 
will  be  found  which  will  permit  the  production  of  potassium  cyanide 
under  conditions  remunerative  both  to  the  producer  and  consumer. 
The  industry  of  the  cyanide  compounds  has  been  developed  especially 
in  Germany  and  in  England;  France  has  remained  somewhat  behind 
in  this  line.  Several  manufacturers  produce  some  cyanide,  to  be 
sure,  but  they  do  not  find  such  an  outlet  for  it  as  they  should  have, 
because  of  the  great  competition  in  the  market  which  the  English 
and  the  Ge  mans  are  making,  and  because  of  the  cheaper  price 
at  which  they  sell  their  product. 

This  condition  of  affairs  attracted  the  attention  of  the  Min- 
ister of  Commerce  and  Manufactures,  and  in  a  letter  of  Dec. 
6,  1897,  addressed  to  the  President  of  the  Council  Chamber  of 
Chemical  Products,  he  called  to  the  attention  of  the  manufactur- 


COMMERCIAL  AND   INDUSTRIAL  STUDY.  71 

ers   the   important  markets  reserved  for  this  branch  of  chemical 
industry. 

The  letter,  as  well  as  the  discussion  which  it  provoked  at  the 
meeting  of  the  Council  Chamber  of  Chemical  Products  on  the  8th, 
of  December  following,  are  here  reproduced: 

PARIS,  December  6,  1897. 
MR.  PRESIDENT: — 

The  export  house  Orosdi  Back,  whose  headquarters  are  in  Paris,  cite- 
d'Hauteville,  No.  9,  recently  called  my  attention  to  the  interest  which  the: 
manufacture  of  potassium  cyanide  would  offer  to  French  industry. 

The  use  of  this  product  in  treating  the  wastes  of  gold-mines  has  giveir 
such  results  that  all  the  mines  are  gradually  making  installations  for  putting; 
this  method  into  practice. 

The  present  sales  of  potassium  cyanide  in  the  Transvaal  and,  the  whole  of 
South  Africa  already  exceeds  3000-4000  tons  per  annum,  and  it  is  expected 
within  two  or  three  years,  when  the  cyanide  process  shall  have  become  general, 
that  the  demand  for  this  product  will  exceed  10,000  tons  in  the  Rand  district 
alone.  If  to  this  amount  be  added  the  quantity  consumed  by  all  the  gold- 
mines in  all  parts  of  the  world,  it  is  seen  that  a  considerable  field  is  open  for 
the  sale  of  this  product,  the  sale  of  which  at  present  is  monopolized  by  England 
and  Germany. 

According  to  Orosdi  Back,  the  cyanide  of  potassium  employed  should 
be  98%,  of  a  pale-yellow  color.  It  is  shipped  in  wooden  boxes  lined  with  zinc, 
holding  100  kg.  The  price  varies  from  190  to  230-240  francs  per  100  kg. 
It  seemed  to  me  that  the  above  data  would  be  of  interest  to  your  association, 
and  I  have  the  honor  of  communicating  them  to  you,  giving  you  the  care 
of  making  them  knowji  to  the  manufacturers  who  might  be  willing  to  use 
them. 

Yours,  etc., 

Minister  of  Commerce,  Industry,  Post,  and  Telegraph. 
For  the  Minister,  by  authority. 

Director  of  Commerce, 

CHANDEZE. 

Council  Chamber  of  Chemical  Products,  sitting  of  Dec.  8,  1897. 
MR.  PRESIDENT: — 

Before  receiving  this  letter  the  Minister  had  already  interviewed  me  on 
this  question,  and  I  explained  to  him  that  the  French  manufacture  of  potas- 
sium cyanide  is  only  enough  for  our  needs,  i.e.,  about  30,000  kg.  per  year; 
that  this  amount  is  produced  y  a  single  firm,  other  manufacturers  who  pro- 
duced it  formerly  having  abandoned  it  because  of  the  unremunerative  price 
obtained  for  it. 

The  price  of  potassium  cyanide  has,  in  fact,  suffered  a  considerable  reduc- 
tion in  the  last  few  years.  At  present  it  is  worth  3  francs  per  kg.  in  France, 
and  2.25  francs  in  England  and  Germany. 


72       THE  PRESENT  CONDITION  OF  THE  CYANIDE  INDUSTRY. 


The  consumption  of  this  product  is  very  great  in  the  Transvaal,  but  the 
figures  3000-4000  tons,  given  by  the  firm  Orosdi  Back,  seem  somewhat  ex- 
aggerated. From  data  which  I  have  received,  the  sales  in  the  Transvaal 
would  amount  to  100  tons  per  month,  and  only  1  ton  in  Madagascar;  but 
the  consumption  of  this  colony  is  destined  to  increase. 

The  company  in  France  which  manufactures  potassium  cyanide  tried  to 
compete  with  foreign  firms  doing  business  in  the  Transvaal,  but  abandoned 
the  attempt  because  it  was  estimated  that  the  sale  price  of  2.25  francs  per 
kilogram  (about  22.5  cents  per  Ib.)  did  not  leave  a  sufficient  profit. 

MR.  GASTON  POULENC: — The  English  have  found,  and  are  now  exploiting, 
processes  for  the  manufacture  of  potassium  cyanide  without  the  use  of  ferro- 
cyanide.  That  is  a  very  great  advantage  when  the  net  cost  is  considered. 
And  this  superiority  will  last  until  our  manufacturers  or  our  chemists  have 
analogous  met  hods. 

MR.  PRESIDENT: — It  seems  to  me,  finally,  that  the  communication  just 
presented  by  our  fellow  member  fully  confirms  the  data  which  I  gave  to  the 
Minister,  and  the  inability  of  the  French  industry  to  compete  successfully 
^t  the  present  time. 

It  is  to  be  hoped  that  in  the  near  future  the  discoveries  of  our  chemists 
will  make  it  possible  for  us  to  regain  this  industry.  The  effort  of  the  inventors 
is  i  this  direction,  and  in  the  last  dozen  years,  both  in  France  and  abroad, 
a  great  number  of  patents  for  the  production  of  this  substance  have  been 
•taken  out. 

Having  made  these  general  observations,  let  us  now  examine  the 
state  of  this  industry  in  the  different  countries  where  cyanide  is 
produced. 

The  following  table  shows  the  production  of  the  different  coun- 
tries in  1899,  according  to  L.  Guillet: 


Country. 

Potassium 
Ferrocyanide. 

Potassium 
Ferricyanide. 

Potassium 
Cyanide. 

Germany  Austria        

tons. 
4,000 

tons. 

tons. 
1  500 

England          •  

3,000 

__ 

2  000 

1,500 

11 

250 

United  States   

1,500 

1  500 

Belgium   Holland           . 

500 

Total  

10,500 

11 

5,250 

France  therefore  produces  l/2i  of  the  total  production  of  cyanides 
and  1/7  of  the  ferrocyanides,  while  Germany  and  England  produce 
more  than  1/2  of  the  total  of  these  two  products. 

The  consumption  is  found  divided  among  the  different  countries. 

Ferrocyanide   of  potassium  which   is  produced  in  France  is  to 


COMMERCIAL  AND  INDUSTRIAL  STUDY.  73" 

a  great  extent  exported  to  Germany  and  England,  where  it  is  trans- 
formed into  the  cyanide.  Germany  herself  exports  a*  great  quantity 
to  the  United  States,  where  for  economic  reasons  it  is  transformed 
into  the  cyanide  of  potassium;  the  remainder  is  us  d  at  the  manu- 
factory for  the  various  needs  of  the  industry.  The  cyanide  is  exported 
to  gold-mines,  notably  to  the  Transvaal,  where  its  consumption 
increases  daily.  Thus  in  1897  the  consumption  in  the  Transvaal 
was  1710  tons;  in  1898  it  had  increased  to  2230  tons;  in  1899  to 
2400  tons.  The  other  gold  districts  consume  but  little  because 
the  beds  are  still  worked  by  the  old  method  and  quite  often  they 
are  not  in  the  hands  of  companies  or  manufacturers,  the  gold  being 
bought  from  individual  workers. 

However  that  may  be,  the  cyanide  method  is  gradually  increasing. 
Several  installations  in  the  United  States,  in  California  and  Alaska, 
have  been  noted,  and  one  can  foresee  that  gradually  the  total  con- 
sumption wi  1  be  considerably  increased. 

The  following  table  gives  the  names  of  the  principal  firms  of 
France  and  other  countries  which  manufacture  or  sell  cyanide  com- 
pounds: 


OF  THE 

UNIVERSITY 

OF 


.74       THE  PRESENT  CONDITION  OF  THE  CYANIDE  INDUSTRY. 


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COMMERCIAL  AND  INDUSTRIAL  STUDY 


75 


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76       THE  PRESENT  CONDITION  OF  THE  CYANIDE  INDUSTRY. 


Manufactured. 

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Manufactured. 

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3UCING  CYANIDE  COMPOUNDS- 
GERMANY  —  Continued. 

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Birmingham 
Sheffield 
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British  Cyanides  Comp 
Cruickshank  
Dolbbe  &  Son  
Foster  &  Son  
Harris  &  Co.,  Limited. 
Hopkins  &  Williams.  . 
Johnson  &  Sons  

COMMERCIAL  AND  INDUSTRIAL  STUDY. 


77 


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78      THE  PRESENT  CONDITION  OF  THE  CYANIDE  INDUSTRY. 


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Hochstetter  & 
Rotlingshofer. 
Engel  und  Becke 


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COMMERCIAL  AND  INDUSTRIAL  STUDY. 


79 


Although  it  is  extremely  difficult  to  obtain  data  from  the  manu- 
facturers concerning  the  production  and  consumption,  the  net  cost, 
•etc.,  we  have,  nevertheless,  been  able  to  procure  a  certain  num- 
.ber  of  documents  bearing  on  these  questions.  The  following  tables 
give  a  sufficiently  correct  idea  of  the  condition  of  the  cyanide  indus- 
tries, and  show  well  the  development  of  this  branch  of  chemical 
industry  during  the  past  few  years. 

FRENCH   IMPORTATIONS   OF    POTASSIUM   FERROCYANIDE   IN 

KILOGRAMS. 


Exporting 

'  Country. 

Year. 

England. 

Germany. 

Belgium. 

Other 
Countries. 

Total. 

Value. 

1887  

168,669 



168 

79,512 

248,349 

347,689 

1888 

186  404 

.  

77,784 

264,288 

343  574 

1889 

150  028 



%   65 

66,660 

216  753 

303,454 

1890 

48086 



65,317 

38,777 

152,180 

243  488 

1891 

100  932 

__ 

28,310 

15,725 

144,967 

260  941 

1$92 

69354 

__ 

52,185 

20,018 

141,557 

254  803 

1893     .   .  . 

50  771 



62,761 

19,529 

133,061 

239  510 

1894   .  .   . 

40079 



42,798 

31,173 

114050 

216  695 

1895   

78,547 



23,079 

20,956 

122,582 

232  906 

1896   

48,501 



49,768 

4,482 

142,751 

228  402 

1897  

29,178 

11,454 

54,736 

1,216 

96,584 

125  559 

1898  

37,266 

9,153 

18,457 

84 

64,960 

87  696 

1899  

15,754 

40,243 

50 

56,047 

86  873 

1900  
1901  (10  months). 

1,654 

12,789 

41,700 

56,143 
113,700 

92,636 
149,000 

AMOUNTS  CONSUMED  IN  EACH  OF  THESE  EXPORTING  COUNTRIES. 


Year. 

England. 

Germany. 

Belgium. 

Other 
Countries. 

Total. 

Value. 

1887  

89,398 

141 

62220 

151,759 

1888 

104  354 

52 

76  699 

181  105 

1889 

84  458 

65 

62  701 

147  224 

1890  

48086 

40 

11  477 

81  822 

1891   . 

69,354 

353 

14  212 

73492 

1892  

50,771 

.  . 

379 

16489 

83  919 

1893  

40,079 

_ 

9887 

782 

67,639 

_ 

1894 

77447 

27 

15  705 

50  478 

1895 

48501 

6441 

32  883 

92  879 

1896  

87825 

1897  

28,939 

8,460 

29 

336 

33  764 

49093 

1898.  

15,363 

20,470 

1899 

12  022 

18  634 

1900 

13  272 

21  899 

1901  (10  months). 

— 

— 

— 

— 

90,200 

149,000 

80      THE  PRESENT  CONDITION  OF  THE  CYANIDE  INDUSTRY. 


FRENCH   EXPORT   OF   POTASSIUM   FERROCYANIDE   IN    KILOGRAMS 

FROM  1897-1900. 


Country. 

1897 

1898 

1899 

1900 

England  

45  339 

115  531 

87  470 

71   A  A  A 

Germany  

41  878 

59236 

miQQ 

4.C1   QO/i 

Belgium 

41  879 

40  017 

ioi,yo'± 

47  979 

Switzerland 

22  293 

OQ  OOQ 

Italy          



17  1R^ 

Other  countries  
Colonies  and  Protectorates 

United  States 

25,136 

5,481 
of  which  2,189 
for  Algeria. 

147,658 

27,933 
21,761 
of  which  20,000 
for  Reunion. 

265,796 

55,580 
3,673 

55  917 

26,108 
3,415 

Spain 

40  328 

Total          

307,371 

512,550 

463  124 

645  697 

Value  in  francs       

403,557 

697,996 

717  842 

1  065  400 

TOTAL    DRENCH   AND    FOREIGN    EXPORTATION    OF    POTASSIUM 
FERROCYANIDE,  1887-1896. 


1887 

1888 

1889 

1890 

1891 

Amount  in  kilograms  . 
Value  in  francs 

122,048 
177,083 

90,426 
118,789 

85,594 
122,898 

127,384 
215  397 

188,628 
363  044 

1892 

1893 

1894 

1895 

1896 

Amount  in  kilograms.  . 
Value  in  francs  .  • 

120,696 
230,074 

184,231 
361,350 

198,769 
406,797 

107,974 
216  986 

139,735 
232  014 

FRENCH    AND    NATIONALIZED    EXPORTATION    OF    POTASSIUM 
FERROCYANIDE,  1887-1896. 


1887 

1888 

1889 

1890 

1891 

117,571 
235,142 

Amount  in  kilograms.  . 
Value  in  francs  

24,867 
41,030 

6,175 
9,263 

15,334 
24,534 

57,912 
104,242 

' 

1892 

1893 

1894 

1895 

1896 

Amount  in  kilograms.  . 
Value  in  francs  

64,092 
128,184 

118,938 
243,823 

145,682 
305,932 

78,907 
161,759 

84,383 
143,451 

PART  THREE. 

METHODS  OF  MANUFACTURING  CYANIDE 
COMPOUNDS. 


GENERAL   CONSIDERATIONS. 

BEFORE  taking  up  the  discussion  of  the  numerous  methods 
for  the  manufacture  of  the  cyanide  compounds,  it  seems  necessary 
to  glance  for  a  moment  at  the  evolution  accomplished  by  these 
methods,  a  very  interesting  evolution,  since  it  has  transformed 
an  industry  which  was  at  first  entirely  subjected  to  the  crudest 
empiricism  to  an  industry  based  on  purely  scientific  data. 

The  industry  of  the  cyanogen  compounds,  like  that  of  the  greater 
part  of  the  chemical  industries,  had  its  origin  in  alchemy.  It  orig- 
inated in  1704,  from  the  discovery  of  Prussian  blue.  This  dis- 
covery, which  was  purely  accidental,  is  due  to  the  Berlin  dyer  Dies- 
bach,  who  obtained  this  compound  by  the  action  of  alum  and  sul- 
phate of  iron  on  the  potash  residues  which  the  then  celebrated 
alchemist  Dippel  had  used  in  the  rectification  of  an  animal  oil  extracted 
from  the  volatile  substances  of  blood. 

From  this  discovery,  Dippel  concluded  that  Prussian  blue  was 
formed  by  the  action  of  iron  on  potassa  which  had  been  brought 
in  contact  with  organic  animal  substances  at  a  certain  temperature. 

The  discovery  of  Diesbach  immediately  became  of  industrial 
importance,  and  Prussian  blue  was  prepared  by  calcining  dried 
beef's  blood,  and  later  meat  or  horns  with  potassium  carbonate. 

The  product  of  this  treatment  was  extracted  with  water,  and 
the  solution  thus  obtained,  called  blood-lye,  was  treated  with  alum 
and  sulphate  of  iron,  giving  Prussian  blue.  This  was  for  a  long 

81 


82         METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

time  the  only  body  known  and  prepared,  and  th's  without  knowing 
exactly  what  was  its  composition  and  its  mode  of  formation. 

In  1752  Macquer,  then  Bergmann  and  Sage,  showed  that  from 
Prussian  blue  a  definite  and  crystallizable  salt  could  be  extracted, 
the  nature  of  which  they  could  not  determine. 

That  Prussian  blue  and  the  salt  obtained  from  blood-lye  were 
compounds  of  cyanogen  was  first  definitely  proven  in  1823  by  Gay- 
Lussac. 

Although  this  was  an  important  discovery,  yet  the  methods  of 
producing  these  compounds  were  not  at  all  changed,  and  for  a  long 
time  the  only  method  employed,  notwithstanding  its  imperfec- 
tions, was  that  of  igniting  nitrogenous  organic  substances  in  the 
presence  of  alkaline  carbonates.  That  method  sufficed,  more- 
over, to  supply  the  limited  demand. 

But,  beginning  with  1837,  a  most  interesting  and  important 
series  of  discoveries  and  researches  in  the  history  of  the  cyanide 
industry  attracted  the  attention  of  investigators  and  manufac- 
turers, and  fixed  in  a  clearer  manner  the  ideas  which  were  being 
formed  concerning  the  formation  of  these  bodies.  The  successive 
discoveries  of  Clark  and  of  Redenbacher,  describing  the  formation 
of  efflorescences  of  potassium  cyanide  in  blast-furnaces,  together 
'  with  the  works  of  Lewis  Thompson,  Desf osses,  Fowner,  and  Young, 
who  obtained  this  same  compound  by  the  action,  at  red  heat,  of 
a  current  of  air  upon  a  mixture  of  potassium  carbonate  and  char- 
coal, gave  birth  to  the  first  principles  of  a  theory  which  at  first 
was  disputed,  but  soon  after  acknowledged  to  be  the  true  one. 

In  fact,  several  -years  later,  Bunsen,  then  Playfair,  and  later 
Riecken,  in  their  investigations  established  clearly  the  role  which 
atmospheric  nitrogen  plays  in  the  formation  of  cyanide  compounds. 

It  is  easy  to  understand  how  this  discovery  attracted  the  atten- 
tion.of  the  manufacturers  when  the  importance  and  the  economic 
aspects  of  the  question  are  considered.  From  that  time  on  they 
exerted  themselves  in  applying  in  a  practical  way  the  results  ob- 
tained by  investigators,  and  numbers  of  patents  followed  each 
other,  all  tending  to  do  away  with  the  use  of  nitrogenous  organic 
matter  (which  is  rather  costly  and  imperfect)  and  approaching  as 
much  as  possible  to  the  synthetic  production,  which  is  simpler  and 
more  economical. 


GENERAL  CONSIDERATIONS.  83 

At  the  present  time  the  tendency  is  still  in  the  same  direction, 
and  one  must  not  despair  of  seeing,  in  the  very  near  future,  the 
success  of  this  important  problem  of  the  fixation  of  atmospheric 
nitrogen  in  the  production  of  cyanide  compounds  on  an  industrial 
scale. 

The  first  efforts  in  this  direction  were  unfortunately  fruitless 
and  therefore  short  lived.  They  were  all  inspired  with  the  same  idea : 
the  passing  of  nitrogen  over  a  suitably  heated  mixture  of  charcoal 
and  an  alkaline  carbonate  or  an  alkali.  Such  are  the  methods  of 
Bunsen,  Ertel,  Armengaud,  Possoz,  and  Boissiere,  Lambilly. 

The  next  step  was  the  replacing  of  the  carbonates  of  the  alkalis: 
by  the  alkali  metal  itself  (Castner,  MacDonald,  Mackey,  Hornig, 
Schneider). 

Other  inventors  made  use  of  ammonia  instead  of  nitrogen.  Quite 
recently,  in  Germany,  processes  have  been  patented  along  this  line,, 
and,  as  will  be  seen  later,  the  results  are  thought  to  be  satisfactory. 

Indirect  means  were  also  tried,  such  as  those  suggested  by  Gelis,. 
and  taken  up  by  Tcherniac  and  Gunzberg,  which  consisted  in  pro- 
ducing ammonium  sulphocyanide,  and  this  was  converted  into  potas- 
sium cyanide. 

In  the  mean  time  the  discovery  of  cyanide  compounds  in  the 
purifying  masses  from  the  manufacture  of  illuminating-gas,  and  in 
sugar-beet  molasses  and  vinasses,  added  a  new  and  lively  interest 
to  this  industry. 

One  must  also  mention  the  use  of  metallic  carbides  recently 
praised  as  a  means  of  fixing  atmospheric  nitrogen  for  the  production 
of  cyanides,  a  tentative  method  which  seems  to  have  given  some 
results. 

That  the  question  is  complex  may  easily  be  seen  from  these  general 
remarks.  It  has  not  yet  been  definitely  solved,  nor  has  the  ideal 
process  been  found.  Nevertheless  certain  modes  of  manufacture 
have  already  furnished  appreciable  results,  and  show  a  real  progress.. 
All  these  will  be  reviewed  in  this  portion  of  this  work. 

The  order  in  which  this  interesting  study  will  be  taken  up  follows 
quite  naturally  from  the  preceding  remarks  and  will  be  as  follows : 

Chapter  VI.  Manufacture  of  Cyanides. 

(1)  Non-synthetic  processes:  (a)  production  by  means  of  f erro- 
cyanides;    (6)    production  by  means  of  sulphocyanides. 


84         METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

(2)  Synthetic  processes :  (a)  the  use  of  atmospheric  nitrogen  ; 

(6)  the  use  of  ammoniacal  nitrogen. 

(3)  Other  processes. 

Chapter  VII.  Manufacture  of  Ferrocyanides. 

(1)  Old  processes. 

(2)  Extraction  of  gas  residues:    (a)  direct  extraction  of  the 

gas;  (6)  extraction  of  ammoniacal  liquors;  (c)  extrac- 
tion of  the  spent  oxides  from  illuminating-gas. 

Chapter  VIII.  Manufacture  of  Ferricyanides. 

Chapter  IX.  Manufacture  of  Sulphocyanides. 

Chapter  X.  Manufacture  of  various  other  cyanide  compounds : 
nitroprussiates,  Prussian  blue,  Turnbull  blue,  etc. 


CHAPTER  VI. 
MANUFACTURE    OF    CYANIDES. 

I.  NON-SYNTHETIC  PROCESSES. 
A.   EXTRACTION  OF  CYANIDES  FROM  FERROCYANIDES. 

Old  Process. — The  oldest  method  of  obtaining  potassium  cyanide, 
a  method  which  is  scarcely  ever  used  except  in  the  manufacture  of 
the  absolutely  pure  salt,  is  that  of  Robiquet,  modified  by  Geiger. 
It  consists  in  igniting  the  dried  yellow  prussiate  or  ferrocyanide  of 
potassium. 

Under  the  influence  of  heat  the  ferrocyanide  of  potassium  is 
decomposed  according  to  the  reaction 

Fe(CN)  6K4  =  4CNK + C2Fe  +  N. 

It  is  absolutely  essential  that  the  ferrocyanide  of  potassium 
used  for  this  purpose  should  be  (1)  perfectly  free  of  sulphate  uf 
potassium,  which  in  the  above  reaction  would  become  transformed 
into  the  sulphide,  which  would  give  a  yellow  color  to  the  cyanide; 
(2)  perfectly  free  from  its  water  of  crystallization,  which  would  tend 
to  retard  the  reaction. 

The  method  of  preparation  is  as  follows:  Yellow  prussiate  is 
first  carefully  dried  at  about  100°  C.  upon  plates  of  sheet  iron  or 
in  cast-iron  pans;  thus  the  dried  product  is  transferred  to  forged- 
iron  crucibles  capable  of  holding  about  80  liters  and  covered  with 
an  iron  lid.  These  crucibles  are  then  placed  in  batteries  of  five  or 
six  in  furnaces. 

Into  each  one  are  placed  80  kilograms  of  ferrocyanide  and  the 
whole  gradually  heated.  Just  as  soon  as  the  product  is  fused,  the 
temperature  is  gradually  raised  to  a  dull  red;  the  whole  is  stirred 

85 


86         METHODS  OF  MANUFACTURING  CYANIDE   COMPOUNDS. 

from  time  to  time  with  a  long-handled  iron  dipper.  The  operation 
lasts  about  seven  or  eight  hours,  and  is  ended  when  a  sample  taken 
out  and  cooled  has  a  white,  dull,  porcelain-like  appearance. 

Care  must  be  taken  that  the  temperature  does  not  go  beyond 
dull  redness,  otherwise  the  cyanide  formed  would  itself  be  decom- 
posed into  potassium  carbide  and  nitrogen. 

2CNK  =  C2K2+N2.* 

When  the  operation  has  been  carefully  carried  out,  the  result  is 
a  mixture  of  carbide  of  iron  and  cyanide  of  potassium,  the  former 
adhering  to  the  sides  of  the  crucible,  the  latter  in  the  midst  of  the 
mass. 

In  order  to  obtain  the  cyanide  from  the  mixture  recourse  may 
be  had  to  decantation  followed  by  filtration  or  to  lixiviation. 

In  the  first  case  the  fused  product  is  decanted  upon  cast-iron 
niters  (A)  (Fig.  1),  the  bottom  of  which  is  a  grate  which  is  covered 
to  about  1/3  of  the  height  of  the  filter  with  iron  turnings.  This  filter 
is  kept  at  dull  redness  during  the  time  of  the  operation.  The  cya- 
nide is  drawn  from  the  crucibles  by  means  of  iron  dippers  and 
poured  upon  the  filter.  The  first  portions  of  the  filtrate  are  often 
contaminated  with  carbide  of  iron;  they  are  therefore  fused  anew 
in  the  crucibles  and  there  refiltered. 

The  filtrate  is  collected  in  polished  and  perfectly  clean  iron  pans 
(C),  which  are  set  in  a  trough  (D)  filled  with  cold  water. 

Too  long  contact  of  the  potassium  cyanide  with  the  iron  carbide 
formed  must  be  avoided,  for  experience  has  shown  that  the  ferro- 
cyanide  was  inclined  to  become  once  more  formed  by  an  inverse 
reaction. 

If  recourse  is  had  to  lixiviation,  the  product  of  ignition  is  taken 
up  either  with  water  or  with  alcohol. 

The  extraction  with  water  is  a  cheaper  but  a  more  delicate 
operation.  Much  care  must  be  taken  and  the  work  carried  on 
rapidly,  because  water  always  decomposes  the  potassium  cyanide, 
forming  ferrocyanide. 

*  It  may  be  remarked  that  it  is  precisely  this  decomposition  of  potassium  cyanide 
at  a  high  temperature  which  renders  it  impossible  to  obtain  the  cyanide  by  means 
of  the  electric  furnace,  as  was  attempted  by  Moissan. 


MANUFACTURE  OF  CYANIDES. 


87 


Although  the  use  of  alcohol  is  quite  costly,  it  is  preferable.  The 
extraction  is  carried  on  in  the  warmth;  it  is  quite  slow  because 
of  the  little  solubility  of  potassium  cyanide  in  alcohol. 

In  each  of  the  above  cases,  the  lixiviation  is  followed  by  evapora- 
tion and  a  rapid  drying  of  the  cyanide.  In  the  case  of  alcohol 
this  solvent  may  be  recovered  and  so  be  used  over  and  over. 

As  may  be  seen  this  process  is  rather  defective.  During  the 
process  notable  quantities  of  cyanogen  in  the  form  of  iron  carbide 
and  nitrogen  are  lost,  and  in  fact  only  about  2/3  of  the  cyanogen 
used  is  recovered;  10  parts  of  ferrocyanide  give  only  7  parts  of 


FIG.  1. — Cyanide-filter. 

cyanide,  i.e.  45  kg.  of  absolutely  pure  cyanide  for  100  kg.  ferrocy- 
anide used. 

Liebig's  Process.— With  a  view  of  remedying  this  objection,. 
Clemm  Rodgers  and  later  Liebig  proposed  igniting  dry  ferro- 
cyanide in  the  presence  of  dry  potassium  carbonate.  This  process, 
is  still  sometimes  used.  Clemm  advised  the  use  of  a  mixture  of 
8  parts  ferrocyanide  and  3  parts  potassium  carbonate.  The  reac- 
tion is  as  follows: 

(1)  Fe(CN)  6K4 + C03K2  =  6CNK  +  FeO + C02,  but  under  the  influ- 
ence of  the  iron  oxide  formed  a  smaU  quantity  of  cyanide  is  trans- 
formed into  cyanate,  so  that  the  reaction  is  in  reality  as  follows: 

(2)  Fe(CN)6K4+C03K2  =  5CNK+CNOK+Fe+C02,   or,    better 
still,  a  combination  of  equations  (1)  andv  (2). 

2Fe(CN)6K4+2C03K2  =  11CNK  +CNOK  +  FeO +Fe  +2C02. 


88        METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

The  product  is  treated  with  water  whereby  a  solution  is  obtained 
consisting  of  cyanide  and  an  excess  of  potassium  carbonate. 

In  order  to  separate  these  bodies,  alcohol  or  acetone  is  added 
which  precipitates  the  insoluble  cyanide. 

The  residue,  consisting  of  iron  oxide,  potassium  carbonate,  iron, 
small  quantities  of  undecomposed  ferrocyanide  and  unprecipitated 
cyanide,  is  powdered  and  allowed  to  stand  in  air.  Under  these 
conditions  insoluble  iron  peroxide  is  formed.  The  product  is  once 
more  extracted,  the  solutions  evaporated,  and  the  residue  ignited. 
In  this  way  a  certain  part  of  the  potassium  carbonate  may  be 
recovered  which  may  be  used  over  again.  Ten  parts  of  ferrocyanide 
give  8.8  parts  cyanide  and  2.2  parts  of  cyanate. 

Wagner's  Process. — In  order  to  avoid  the  formation  of  cyanate 
at  the  expense  of  cyanide,  Wagner  proposed  igniting  the  mixture 
of  ferrocyanide  and  alkali  carbonate  with  a  small  quantity  of  finely 
pulverized  wood  charcoal  the  use  of  which  is  to  reduce  any  cyanate 
formed.  The  following  are  the  amounts  proposed  by  Wagner: 

Ferrocyanide  of  potassium 8      parts. 

Carbonate  of  soda 2 

Powdered  wood  charcoal 0.2  part. 

The  reaction  is 
Fe(CN)  6K4 + C03Na2 + C = 4CNK + 2CNNa + Fe  +  C02  +  CO. 

Another  advantage  of  this  method  would  be  the  separation  of 
iron,  which  would  be  easier.  The  mixture  thus  obtained  is  formed 
by  4  mol.  of  potassium  cyanide  and  2  mol.  sodium  cyanide.  Later 
will  be  discussed  the  advantage  which  this  mixture,  which  is  richer 
in  cyanogen,  has  over  potassium  cyanide  alone. 

Chaster's  Process. — This  is  only  a  modification  of  Wagner's 
process,  and  consists  in  adding  to  the  mixture  of  ferrocyanide  car- 
bonate and  charcoal  a  certain  amount  of  tar,  pitch,  or  bitumen. 
The  yield  is  thus  somewhat  greater,  the  reaction  being  carried  on 
in  the  reducing  atmosphere  produced  by  the  hydrocarbons  added. 

The  following  are  the  proportions  proposed  by  Chaster: 

Anhydrous  ferrocyanide 65-75  parts. 

Carbonate 20     " 

Wood  charcoal. .  5     ' c 


MANUFACTURE  OF  CYANIDES.  89 

The  ferrocyanide  and  carbonate  are  ground  together  and  during 
the  grinding  5%  dried  wood  charcoal  is  added,  together  with  a 
quantity  of  tar,  pitch,  bitumen,  or  asphaltum  or  any  other  analogous 
substance  sufficient  to  give  the  whole  mass  the  consistency  of  a 
paste  or  of  mortar.  In  case  the  mass  may  not  be  plastic  enough 
a  small  quantity  of  benzine  or  petroleum  is  added. 

This  mass  is  compressed  into  the  form  of  briquettes,  which  are 
ignited  in  a  furnace  with  a  reducing  flame. 

Notwithstanding  these  modifications,  processes  which  are  based 
on  the  decomposition  of  ferrocyanide  under  the  influence  of  heat 
are  not  profitable.  They  are  rather  costly;  the  losses  in  nitrogen, 
in  alkali,  and  even  in  cyanide  by  volatilization  are  sometimes  con- 
siderable. 

Their  industrial  use  haSv  always  been  most  limited.  In  trying  to 
perfect  these  processes,  many  very  ingenious  modifications  have 
been  devised  which  have,  it  seems,  given  good  results,  and  the 
industrial  use  of  which  has,  latterly,  been  quite  extensive. 

The  Process  of  Rossler  and  Hasslacher  (of  New  York). — The  type 
of  these  new  modifications  is  that  of  the  house  of  Rossler  und  Hass- 
lacher of  New  York,  belonging  to  the  Deutsch  Gold  und  Silber 
Scheide  Anstalt.  This  process,  which  was  proposed  by  Erlenmeyer, 
is  based  upon  the  action  of  metallic  sodium  on  potassium  cyanide, 
according  to  the  reaction  / 

Fe(CN)6K4+Na2  =  Fe+4(CNK),2(CNNa). 

The  product  is  then  treated  with  water  and  the  solution  evaporated. 

The  product  thus  obtained,  which  is  sold  as  potassium  cyanide 
98-100%,  is  in  fact  but  a  mixture  of  4  mol.  of  potassium  cyanide 
with  2  mol.  sodium  cyanide,  a  product  identical  with  that  produced 
by  Wagner's  process.  If  the  whole  be  assumed  as  potassium  cyanide, 
it  is  seen  that  it  contains  98%  of  the  cyanogen  used.  Moreover, 
this  mixture  has  the  advantage  of  being  richer  in  cyanogen  than  is 
the  potassium  cyanide,  because  the  atomic  weight  of  sodium  is. 
less  than  that  of  potassium.  Thus  109  grams  of  this  mixture  cor- 
responds to  106  grams  of  potassium  cyanide. 

Besides  having  the  advantage  of  avoiding  loss  of  cyanogen,  this 
method  permits  the  use  of  metallic  sodium,  a  metal  which,  since- 


90         METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

Deville's  process  for  the  manufacture  of  aluminium  was  abandoned, 
found  but  little  use  in  the  arts. 

At  present,  sodium  is  produced  on  a  large  scale  by  electrochem- 
ical industries;  it  is  therefore  of  interest  to  call  attention  to  this 
method  of  application.  This  process  is,  moreover,  in  considerable 
use  in  England,  Germany,  and  even  in  France. 

Wichmann  and  Vautin's  Process.— Because  sodium  was  still 
rather  expensive,  attempts  were  made  to  replace  it  with  alloys  of 
alkali  metals  with  lead.  These  alloys  are  at  the  present  time 
obtained  much  cheaper  than  the  alkali  metals,  by  subjecting  fused 
alkali  chloride  to  electrolysis  in  a  bath  of  melted  lead,  which  acts  as 
a  cathode. 

In  order  to  obtain  potassium  cyanide,  a  mixture  of  potassium 
ferrocyanide  with  a  lead-potassium  alloy  is  used.  If  the  sodium 
cyanide  be  desired,  sodium  ferrocyanide  and  a  lead-sodium  alloy 
are  taken. 

As  in  the  Rossler  and  Hasslacher  process,  a  double  cyanide  of 
sodium  and  potassium  may  be  prepared,  by  causing  an  alloy  of 
lead  sodium  to  act  upon  potassium  ferrocyanide,  or  a  lead-potassium 
alloy  to  act  upon  sodium  ferrocyanide. 

The  dehydrated  ferrocyanide  is  first  pulverized  and  then  mixed 
with  the  powdered  alkaline  alloy.  The  grinding  of  these  alloys  is 
easy  enough,  because  they  are  generally  brittle.  Ordinarily  the 
grinding  is  done  in  the  presence  of  a  small  quantity  of  mineral  oil, 
the  use  of  which  prevents  oxidation. 

The  mixture  is  fused  in  furnaces  at  as  low  a  red  heat  as  possible. 
This  fusion  should,  of  course,  be  done  out  of  contact  with  air.  When 
the  reaction  is  finished,  there  remains  a  fused  mass  consisting  of 
cyanide  as  well  as  iron  and  spongy  lead. 

These  two  foreign  substances  are  separated  from  the  cyanide  by 
decantation  or  by  filtration.  The  mass  may  likewise  be  treated 
with  water,  and  after  filtration  the  solution  of  cyanide  may  be  evap- 
orated. The  lead  and  the  iron  may  also  be  separated.  In  order  to 
do  this,  the  mixture  is  melted  on  an  inclined  plane,  when  the  lead, 
which  is  more  fusible,  runs  off  first,  leaving  the  iron  behind,  or  else 
the  mixture  is  finely  divided  and  stirred  in  a  bath  of  melted  lead, 
which  retains  the  lead  which  was  mixed  with  the  iron,  thus  permit- 
ting the  iron  to  be  collected.  This  iron  may  then  serve  in  the  prepa- 


MANUFACTURE  OF  CYANIDES.  91 

ration  of  ferrocyanides.     The  lead  is  itself  used  anew  in  the  prepa- 
ration of  the  alkaline  alloy. 

The  proportion  of  ferrocyanide  to  alloy  to  be  used  depends  on 
the  quantity  of  alkali  metal  which  the  alloy  contains.  The  authors 
claim  that,  in  practice,  an  alloy  containing  10%  of  alkali  metal  is 
the  best  adapted.  It  is,  however,  always  better  to  use  a  somewhat 
larger  quantity  than  is  theoretically  sufficient  in  the  substitution 
of  the  alkali  metal  for  the  iron  of  the  ferrocyanide.  In  practice,  in 
order  to  prepare  a  double  cyanide  of  sodium  and  potassium,  10 
parts  by  weight  of  the  dehydrated  potassium  ferrocyanide  and  13 
parts  of  the  10%  lead-sodium  alloy  may  be  used. 

A  modification  of  this  process  has  been  proposed  by  Hetherington, 
Hurter,  and  Muspratt  (English  patent  March  20,  1894,  March  1895) ; 
it  consists  in  melting  the  alkaline  alloy  under  a  certain  thickness  of 
cyanide  obtained  in  a  previous  operation,  and  adding  to  this  mix- 
ture, in  small  portions,  the  dried  ferrocyanide.  These  inventors 
recommend  using  an  alloy  with  13%  sodium.  When  the  reaction  is 
complete  the  final  product  is  found  in  three  separate  layers — melted 
lead,  reduced  iron,  and  alkalicyanide,  which  are  easy  of  separation. 
The  lead-sodium  alloy  may  be  replaced  by  the  lead-potassium  alloy, 
but  the  former  is  preferable. 

Does  the  use  of  alkaline  alloys  possess,  as  stated  by  the  inventors 
of  various  patents  on  this  subject,  a  distinct  advantage  over  the 
use  of  alkali  metals  alone?  This  question  is  not  so  easily  answered. 
It  cannot  be  denied,  in  view  of  the  ease  with  which  the  alloys  are 
obtained,  that  the  potassium-lead  alloys,  and  more  especially  the 
sodium-lead  alloys,  are  much  cheaper,  all  things  being  equal  other- 
wise, than  the  same  alkali  metals  themselves.  From  this  point  of 
view  the  processes  of  Vautin  and  Hetherington  would  possess  ad- 
vantages. But,  on  the  other  hand,  one  has  a  right  to  ask,  What  is 
the  role  played  by  the  lead  in  these  reactions?  It  is  known  that 
lead  has  but  a  slight  affinity  for  the  cyanides,  and  that  is  the  reason 
why  lead  cyanide  has  never  been  prepared. 

The  use  of  alkali  cyanides  has  even  been  praised  as  a  means  of 
reducing  lead  carbonate  to  the  metallic  state.  It  becomes  evident, 
therefore,  that  in  the  action  of  lead-sodium  alloy  on  alkali  ferrocya- 
nide, sodium  alone  enters  into  the  reaction. 

Since  the  content  of  the  alkali  metal  in  the  alloys  is  generally 


92        METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

about  13%,  in  order  to  produce  the  same  result  as  100  parts  of  so- 
dium one  must  use  770  parts  of  the  lead-sodium  alloy.  Therefore  the 
net  cost  of  lead-sodium  alloys  containing  13%  sodium  should  be  7.7 
times  less  than  that  of  metallic  sodium,  in  order  that  such  processes 
as  those  of  Vautin  and  of  Hetherington,  etc.,  may  possess  pecu- 
niary advantages  over  those  processes  represented  by  Rossler-Hass- 
lacher,  etc.  The  cost  of  the  alloy  must,  indeed,  be  even  cheaper, 
because  in  the  first  processes  one  must  also  reckon  the  expenses  due 
to  the  separation  of  the  iron  and  the  lead  in  order  to  recover  the 
latter.  Now  then,  according  to  data  on  this  subject,  the  price  of 
lead-sodium  alloys  containing  12-15%  sodium  is  not  so  low,  in 
fact  it  is  only  one  fifth  of  the  price  of  metallic  sodium,  the  price  of 
sodium  taken  into  account  being  that  made  especially  to  manufac- 
turers of  cyanides. 

It  would  seem,  moreover,  that  the  advantage  in  using  alkali 
alloys  is  rather  in  the  case  of  working  and  manipulating  the  prod- 
ucts. In  this  case,  one  must  assume  that  the  lead  is  either  a  reduc- 
ing agent  preventing  the  formation  of  cyanates,  or  simply  a  diluting 
agent  (when  it  is  considered  that  it  forms  87%  of  the  alloy)  whose 
r61e  would  be  to  prevent  the  sodium  from  floating  on  top  of  the  mass 
of  melted  ferrocyanide  and  thus  not  enter  the  reaction. 

In  these  two  cases  the  advantage  offered  by  the  alkali  alloys 
would  be  especially  valuable  from  the  point  of  view  of  the  yield  in 
cyanide. 

Dalinot's  Process. — This  also  depends  on  the  action  of  an  alkali 
metal  on  ferrocyanide,  but  in  this  case  the  metal  is  no  longer  used 
in  the  free  state;  it  is  produced  in  the  nascent  state  during  the 
reaction. 

In  a  suitable  vessel,  and  at  the  required  temperature,  place 
dried  ferrocyanide  mixed  with  sodium  hydroxide  or  with  potas- 
sium hydroxide  in  as  dry  a  state  as  possible.  To  this  mixture  add 
finely  pulverized  calcium  carbide.  The  ingredients  should  be 
added  in  atomic  proportions. 

As  is  well  known,  calcium  carbide  possesses  remarkable  reducing 
properties.  Under  the  conditions  just  mentioned  it  acts  upon 
the  only  body  containing  oxygen,  that  is  the  alkali,  and  sets  the 
metal  free. 

This  reaction  is  the  result  of  the  well-known  fact  that  sodium 


MANUFACTURE  OF  CYANIDES.  93 


unites  with  oxygen,  producing  NaO  +  100  calories,  while  calcium 
combines  with  oxygen,  forming  CaO  +  135  calories.  Consequently 
the  calcium  removes  the  oxygen  from  the  sodium  hydroxide,  leaving 
lime  and  metallic  sodium. 

The  sodium  is  found  in  the  mass  in  the  molecular  state.  It 
comes  in  contact  with  the  cyanogen  which  was  united  to  the  iron, 
and  which  has  been  set  free  in  consequence  of  the  ignition  of  the 
ferrocyanide. 

In  accordance  with  the  law  that  the  most  stable  body  is  the 
one  first  formed,  sodium  cyanide  is  produced,  the  reaction  being 

FeCy6K4+Na20+C2Ca 

=  4KCy  +  2NaCy  +  CaO  +  Fe  +  various  carbides. 

During  the  operation  an  energetic  stirring  of  the  fused  mass  is- 
maintained  so  as  to  have  perfect  contact.  When  the  operation  is 
over,  the  fused  mass  is  filtered  through  a  hot  filter  in  order  to  sepa- 
rate the  residue  of  iron  and  lime. 

Instead  of  the  caustic  alkalis,  the  alkali  carbonates  may  like- 
wise be  used. 

The  calcium  carbides  should  be  quite  dry.  For  this  purpose 
it  is  ground  in  a  grinder  whose  interior  is  perfectly  sheltered  from 
the  atmosphere,  and  is  in  air-tight  communication  with  a  reservoir 
containing  sulphuric  acid.  This  procedure  does  not  lack  in  origi- 
nality, but  its  working  does  not  seem  to  be  very  practical.  It  is 
quite  difficult,  in  fact,  to  obtain  an  alkali  completely  free  of  water,. 
whence  comes  a  loss  in  cyanide  compounds  under  the  form  of  ammo- 
nia. On  the  other  hand,  calcium  carbide  of  commerce  is  frequently 
impure  and  gives  to  the  cyanide  a  more  or  less  intense  coloration,. 
injuring  the  commercial  value  of  this  product. 

Adler's  Process.  —  This  process  was  patented  in  July,  1900,  and  is: 
but  an  improvement  on  that  of  Liebig.  With  the  object  of  reducing 
the  cyanates,  Adler  no  longer  employs  charcoal  but  alkali  ferro- 
cyanides  according  to  the  reaction: 

(1)  FeCy6K4+C03K2  =  4KCy+2KCyO+CO+Fe. 

(2)  2KCyO  +  2FeCy  6K4  =  lOKCy  +  2FeO  +  4C  +  4N. 

(3)  2FeO+2C  =  2CO+2Fe. 


94         METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

368  parts  of  dry  ferrocyanide  of  potassium  are  fused  with  138 
parts  of  dry  potassium  carbonate,  and  toward  the  end  of  the  reac- 
tion 736  parts  of  dry  ferrocyanide  are  added  a  little  at  a  time.  An 
abundant  froth  produced  by  the  reaction  of  the  cyanate  is  at  first 
formed. 

When  the  mass  is  in  a  tranquil  fusion,  it  is  filtered  in  order  to 
separate  the  cyanide  formed  from  the  impurities  —  iron,  oxide  of 
iron,  etc. 

Etard's  Process.  —  This  process  is  connected  rather  with  the 
extraction  of  cyanides  from  sulphocyanides,  since  it  consists  in 
removing  the  sulphur  of  the  sulphocyanides  by  means  of  the  iron 
of  the  ferrocyanides  according  to  the  reaction 

Fe(CN)6K4+CNSK  =  FeS+5CNR4-C2N2. 

In  practice  the  perfectly  dry  ferrocyanide  is  fused  with  the 
equally  dry  sulphocyanide.  Sulphide  of  iron  is  formed,  which 
is  deposited  during  quiet  fusion.  The  cyanide  formed  is  decanted 
hot;  the  cyanide  gas  which  is  set  free  is  not  lost,  but  collected  in 
an  alkaline  solution.  The  mass  may  likewise  be  taken  up  by  water, 
methyl  alcohol,  or  ethyl  alcohol.  In  the  first  case,  work  is  carried 
on  as  rapidly  as  possible  out  of  contact  with  air,  in  order  to  avoid 
the  formation  anew  of  the  ferrocyanides.  In  order  to  avoid  the 
formation  of  the  cyanide  gases  and  consequently  to  increase  the 
yield,  carbonate  of  potassium  may  be  added  to  the  mixture  of  ferro- 
cyanide and  sulphocyanide.  The  reaction  is  then  as  follows: 


Fe(CN)6K4+CNKS+C03K2=FeS  +  7 

368  97  138  455 


In  this  wise,  7  molecules  of  cyanide  of  potassium  are  obtained 
instead  of  5  molecules,  as  in  the  previous  reaction. 

Bergmann's  Process.  —  This  process,  which  is  one  of  little  prac- 
tical value,  and  which  produces  only  the  cyanides  of  copper  and 
silver,  is  a  wet  method 

It  consists  in  heating  a  solution  of  ferrocyanide  in  the  presence 
of  a  copper  or  a  silver  salt,  in  sufficient  quantity  to  effect  the  total 
union  of  the  cyanide  of  the  prussiate  with  the  copper  or  the  silver. 


MANUFACTURE  OF  CYANIDES.  95 

The  mixture  should  contain  a  certain  proportion  of  free  acid, 
which,  producing  the  decomposition  of  the  ferrocyanide,  causes 
the  formation  of  prussic  acid,  which  unites  with  the  silver  or  with 
the  copper  to  form  cyanides  of  these  metals. 

In  the  case  of  the  cyanide  of  silver  the  reaction  is  as  follows: 

6N03Ag  +  FeCy6K4  =  GCyAg + 4N03K  +  (N03)  2Fe. 

422  parts  by  weight  of  crystallized  ferrocyanide  of  potassium 
are  dissolved  in  50  times  its  weight  of  water,  to  which  is  added  a 
2%  solution  of  1020  parts  of  nitrate  of  silver.  After  slightly  acidify- 
ing with  sulphuric  acid,  the  solution  is  brought  to  a^boil  until  the 
whole  of  the  precipitate  of  ferrocyanide  of  silver  which  is  first  formed 
is  completely  transformed  into  cyanide  of  silver  by  absorbing  the 
whole  of  the  silver  remaining  in  excess.  This  cyanide  is  separated 
by  decantation  and  washings. 

In  the  case  of  the  copper  cyanide  the  reaction  may  be  expressed 
thus: 

6S04Cu  +  FeCy6K4  +  3S02  +  6H20 

=  3CuCy2  +  2S04K2  +  S04Fe + 6S04H2. 
7. 

In  order  to  avoid  a  too  excessive  action  of  the  6  molecules  of 
free  sulphuric  acid  which  are  formed  in  the  course  of  the  reaction 
it  is  well  to  operate  in  very  dilute  solution,  or  to  neutralize  the  acid 
as  fast  as  it  is  formed  by  the  addition  of  alkali.  Likewise  a  sul- 
phite may  be  used  from  the  beginning.  At  first  a  reddish-brown 
precipitate  of  ferrocyanide  of  copper  is  formed,  which  under  the 
action  of  heat  is  gradually  transformed  into  a  white,  flucculent 
cyanide  of  copper. 

The  cyanide  of  copper  thus  obtained  furnishes  very  interesting 
double  cyanides  when  digested  in  the  cold  with  an  alkaline  sul- 
phide. 

B.    EXTRACTION   OF   CYANIDES   FROM   SULPHOCYANIDES. 

Sulphocyanides  have  but  a  very  limited  market.  They  consti- 
tute, as  will  be  seen  later,  one  of  the  most  important  residues  in 
the  manufacture  of  illuminating-gas.  Moreover,  for  a  certain  time, 
they  formed  the  basis  of  several  methods  of  cyanide  manufacture, 


96         METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

due  to  the  remarkable  works  of  Caro,  Conroy,  and  of  Playfair,  who 
demonstrated  that  they  could  be  a  profitable  source  of  cyanide 
production. 

Thus,  for  a  long  time,  attempts  have  been  made  to  transform 
these  salts  into  cyanides  or  into  ferrocyanides,  which  find  a  more 
extended  application.  The  interest  taken  in  this  subject  is  well 
shown  by  the  numerous  studies,  and  the  various  patents  taken. 

Theoretically,  this  conversion  of  sulphocyanides  into  cyanides 
appears  quite  simple.  If  the  formula  of  sulphocyanide  of  potassium 
is  taken,  for  example,  one  sees  that  its  conversion  into  cyanide  is 
made  by  the  simple  removal  of  the  atom  of  sulphur  which  it  con- 
tains : 

CNSK-S  =  CNK. 

There  are  two  general  methods  which  may  be  used  in  producing 
such  a  result.  The  first  is  one  of  reduction,  in  which  case  a  sul- 
phide is  formed 

CNSK+R=CNK+RS. 

The  second,  on  the  contrary,  consists  in  removing  the  sulphur 
by  oxidizing  it  with  production  of  a  sulphate: 

CNSK  +  R  +  04  =  S04R + CNK. 


I.  METHODS  OF  OXIDATION. 

This  method  of  treatment  is  the  oldest,  but  it  has  never  been 
used  on  an  industrial  scale. 

The  first  attempt  along  this  line  was  made  by  Hadow,  who  used 
permanganate  of  potash  and  peroxides  of  lead  and  manganese. 
In  a  method  for  the  determination  of  sulphocyanides  by  means 
of  permanganates,  Erlenmeyer  showed  that  in  an  acid  solution 
the  reaction  takes  place  quantitatively: 

5CNSK + 6Mn04K + 4H2S04  =  5KCN  +  6S04Mn + 3S04K2  +  4H20. 

This  method  is  entirely  demonstrated,  but  the  high  cost  of  per- 
manganate was  a  serious  obstacle  to  its  industrial  application.  Never- 
theless, this  discovery  of  Erlenmeyer  caused  '  an  awakening  of 


MANUFACTURE  OF  CYANIDES  97 

ideas.    Alt  showed  that  in  the  presence  of  barium  chloride,  using 
HNOa  as  oxidizing  agent,  the  reaction  is  likewise  quantitative. 

The  ingenious  attempts  of  Parker  and  of  Robinson  (1888-1889) 
must  also  be  mentioned.  The  latter  made  use  of  electrolysis.  He 
passed  the  electric-  current  through  a  solution  of  sulphocyanide 
in  sulphuric  acid.  Prussic  acid,  CNH,  was  formed,  which  was 
collected  in  an  alkaline  solution.  The  causes  of  failure  of  such 
processes  may  be  easily  understood.  The  prussic  acid  set  free  was 
a  continual  source  of  danger  to  the  employes  on  account  of  its  great 
toxicity. 

Raschen's  Methods. — The  next  attempt  was  the  use  of  nitric 
acid  as  oxidizing  agent  under  certain  fixed  conditions.  Such  are 
the  processes  of  Raschen  and  Brock,  worked  by  The  United  Alkali 
Co.,  Limited.  To  the  kindness  of  Dr.  J.  Raschen,  Director  of  The 
United  Alkali  Co.,  Limited,  we  owe  a  complete  description  of  his 
processes,  which  is  reproduced  in  full.  In  the  first  of  these  processes 
the  line  of  procedure,  as  indicated  in  the  patents  taken  out  by 
Brock  and  Raschen  (1888,  1895,  1896),  is  as  follows:  A  20-30% 
solution  of  dry  sodium  or  calcium  sulphocyanide  is  used.  A  definite 
quantity  of  hot  water,  or,  better  still,  of  mother-liquor  from  a  pre- 
vious operation,  is  placed  in  a  hermetically  closed  boiler  provided 
with  a  stirrer  and  the  solution  is  heated  to  96°.  The  stirrer  is  then 
set  in  motion  while  at  the  same  time  the  solution  of  sulphocyanide 
and  nitric  acid  are  added.  The  addition  of  these  two  solutions 
must  be  so  regulated  that  there  is  always  a  slight  excess  of  the  acid  in 
the  mixture.  The  whole  of  the  sulphur  of  the  sulphocyanide  is 
oxidized  into  sulphuric  acid,  while  at  the  same  time  a  mixture  of 
nitrous  acid,  water-vapor,  nitrogen  , oxide  carbonic  acid,  and  hydro- 
cyanic acid  is  set  free.  These  acids  are  passed  through  a  scrubber 
containing  water  at  80°  C.,  which  absorbs  the  nitrous  acid.  After 
having  undergone  this  first  purification  and  having  been  cooled, 
the  gaseous  mixture  passes  into  an  absorption  apparatus  dividedin  to 
two  compartments.  The  first  contains  cold  water,  which  absorbs  a 
great  portion  of  the  hydrocyanic  acid,  allowing  the  carbonic  acid 
and  the  nitrogen  oxide  to  pass  on;  the  second  contains  milk  of 
lime,  which  retains  the  carbonic  acid  and  the  remainder  of  the 
hydrocyanic  acid,  so  that  at  the  outlet  of  the  apparatus,  nitrogen 
oxide  escapes,  which,  mixed  with  air,  is  recovered  under  the  form 


98         METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

of  nitric  acid,  capable  of  being  used  again  in  the  same  process.  The 
solution  of  calcium  cyanide  in  the  second  compartment  is  filtered 
from  the  precipitate  of  the  carbonate  of  lime  and  converted  into 
alkali  cyanide  by  double  decomposition.  The  solution  of  hydro- 
cyanic acid  in  the  first  compartment  is  neutralized  by  means  of 
an  alkaline  solution,  forming  an  alkali  cyanide.  The  cold  water  of 
the  first  compartment  may  equally  well  be  replaced  by  an  alkaline 
solution.  It  is  of  the  utmost  importance  that  the  operation  be 
carried  on  absolutely  out  of  contact  with  air,  otherwise  the  nitrogen 
oxide,  would  become  oxidized  with  the  formation  of  nitrogen  per- 
oxide, which  latter  would  be  absorbed  by  the  alkaline  solution,  form- 
ing nitrite  and  nitrate,  which  would  contaminate  the  cyanide  and 
so  be  a  serious  hindrance  to  the  fusion  of  this  compound,  the  mix- 
ture of  cyanide  and  nitrate  reacting  with  violence. 

It  is  likewise  necessary  because  of  the  extreme  toxicity  of  the 
prussic  acid  to  work  very  carefully  and  to  maintain  a  slight  vacuum 
in  the  apparatus,  so  that  no  gas  shall  escape  into  the  air  if  the 
apparatus  should  leak. 

Raschen  and  Brock  modified  this  process  by  using  mineral  oxi- 
dizing agents,  such  as  the  nitrates,  chromates,  peroxides  of  lead 
or  of  manganese  in  the  presence  of  sulphuric  acid.  With  the  water 
is  mixed  the  acid  and  the  oxidizing  agent  and  the  whole  brought  to 
a  boil;  then  is  added,  little  by  little,  the  sulphocyanide  dissolved 
in  water.  It  is  necessary  to  use  a  somewhat  larger  quantity  of 
oxidizing  agent  and  acid  than  the  theoretical  amount  indicated 
by  the  following  reaction,  using  sulphocyanide  of  sodium  as  an 
example: 

CNSNa + 3S04H2  +  3Mn02  -  CNH + S04NaH  +  S043Mn  +  2H20. 

Toward  the  end  a  little  more  heat  is  applied  in  order  to 
drive  off  completely  the  whole  of  the  hydrocyanic  acid.  The 
gaseous  mixture  is  collected  and  purified,  as  before.  In  the  Wigg 
works  at  Runcorn,  which  belong  to  The  United  Alkali  Co.,  Limited* 
this  process  slightly  modified  is  in  use  at  the  present  time  on  a 
large  scale. 

Raschen  and  Brock  have,  in  fact,  found  that  better  yields  (96%- 
99%  of  theoretical)  are  obtained  if  more  dilute  solutions  be  used 
(170  grams  per  liter),  and  if  the  solution  of  sulphocyanide  be  poured 


MANUFACTURE  OF  CYANIDES.  99 

slowly  into  the  dilute  and  boiling  nitric  acid.  At  Runcorn  sodium 
sulphocyanide  is  used,  besides  sodium  nitrate  and  sulphuric  acid, 
which  latter  act  as  oxidizing  agent. 

The  apparatus  used  in  the  decomposition  consist  of  stoneware 
carboys  A\,  A2,  A3,  ...  An,  placed  in  series,  connected  with  each 
other  by  means  of  earthenware  tubes  starting  at  about  mid-height 
of  one  carboy  and  .ending  in  the  next  at  the  bottom.  Each  one  of 
them  carries,  besides,  an  outlet  tube  B  and  a  tube  C  for  the  inlet 
of  the  steam,  which  latter  tube  serves  as  stirrer. 

First  the  carboys  are  filled  with  dilute  sulphuric  acid,  then 
steam  is  let  on  so  as  to  reach  nearly  the  boiling-point.  Then  the 
solutions  of  sulphocyanide  (170  grams  per  liter)  and  sodium  nitrate 
are  run  in  simultaneously.  The  letting  in  of  steam  and  of  solutions 
is  so  regulated  that  the  temperature  always  remains  constant,  and 
the  liquid  passing  from  the  first  into  the  second  carboy  no  longer 
contains  traces  of  sulphocyanide,  and  the  liquid  of  the  last  carboy 
is  free  from  hydrocyanic  acid.  The  gases  which  are  liberated  are 
chiefly  hydrocyanic  acid  and  nitrogen  dioxide  together  with  a  little 
carbonic  acid,  nitrous  acid,  and  considerable  amounts  of  water- 
vapor.  The  gases  pass  first  into  the  tower  D,  filled  with  quartz 


FIG.  2. — Raschen's  Apparatus. 


pebbles,  through  which  they  pass  from  bottom  to  top,  where  they 
meet  a  shower  of  cold  water  circulating  in  the  opposite  direction, 


100       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

which  absorbs  the  oxides  of  nitrogen,  without  absorbing  the  hydro- 
cyanic acid,  because  the  temperature  has  not  been  lowered.  The 
water- vapor  is  condensed  in  an  ordinary  condenser  E-,  it  carries 
with  it  a  small  quantity  of  hydrocyanic  acid,  which  is  neutralized 
with  caustic  soda. 

At  their  outlet  the  gas  shows  75°-80°  F.  They  are  conducted 
into  the  two  cast-iron  absorbers  CiC2,  which  are  cooled  on  the  out- 
side and  which  contain  caustic  alkali.  The  hydrocyanic  acid  is 
absorbed,  and  the  nitrogen  dioxide  is  set  free  unaltered.  This  latter 
gas  is  brought  in  contact  with  air  in  order  to  recover  the  nitric  acid, 
The  recovery  of  this  gas  is  done  by  passing  the  gas  mixed  with  an 
excess  of  air  through  two  towers  of  refractory  stoneware  M  and  N, 
which  inclose  quartz  pebbles,  and  into  which  falls  a  shower  of  cold 
water. 

The  amount  of  water  and  the  volume  of  air  used  in  the  reaction 
should  be  carefully  regulated  in  order  to  recover  an  acid  of  uniform 
concentration.  However,  it  is  necessary  to  have  an  excess  of  air 
over  the  theoretical  quantity.  This  excess  of  air  carries  a  part  of 
the  heat  liberated  by  the  oxidation  of  the  nitrogen  dioxide  and 
serves  as  a  refrigerating  agent.  The  mixture  of  acid  thus  recovered, 
on  coming  out  of  the  second  tower  is  conducted  directly  into  the 
first  decomposition  carboy,  where  it  oxidizes  a  new  quantity  of  sulpho- 
cyanide. 

The  whole  circulation  of  the  gases  is  made  certain  by  Koerting 
Injectors. 

The  last  operation  is  the  evaporation  of  the  cyanide  solution  in 
order  to  have  a  commercial  product.  This  procedure  is  easily  ac- 
complished in  the  laboratory,  but  quite  difficult  on  an  industrial 
scale.  In  fact  the  evaporation  of  large  amounts  of  cyanide  solu- 
tions always  causes  a  more  or  less  complete  transformation  of  cyano- 
gen into  ammonia.  This  loss  is  chiefly  due  to  the  action  of  super- 
heated steam  in  the  cyanide  mass.  This  objection  may  be  easily 
removed  by  evaporating  the  solution  in  vacuo  and  by  keeping 
it  constantly  stirred.  The  product  obtained  under  these  conditions 
is  a  white  powder  more  or  less  agglomerate.  It  is  free  of  sulphur 
and  therefore  particularly  suitable  in  the  extraction  of  gold.  It 
contains,  however,  several  impurities,  due  mainly  to  the  caustic 
solutions  used.  «T.  T.  Conroy,  who  has  made  a  thorough  study  of 


MANUFACTURE  OF  CYANIDES.  101 

Raschen's  process,*  states  that  the  precautions  taken  in  order  to 
avoid  any  liberation  of  such  toxic  gases  as  hydrocyanic  acid  and 
nitrogen  dioxide  are  perfect,  and  the  total  absence  of  any  odor  in 
the  works  is  a  convincing  proof. 

Beringer's  Process. — Having  studied  thoroughly  the  conversion 
of  sulphocyanides  into  cyanides  by  the  oxidation  process,  Beringer 
discovered  that  the  formation  of  carbonic  acid  was  due  to  the  pres- 
ence of  free  mineral  acids,  and  thereupon  conceived  a  process  whose 
object  is  to  carry  on  the  reaction  in  such  a  manner  as  to  form 
no  free  acid,  or  at  least  if  any  be  formed,  its  effect  is  not 
perceptible. 

In  order  to  do  this  he  uses  nitric  acid  in  sufficient  quantity, 
but  in  the  form  of  nitrate  (of  calcium  or  of  barium).  By  causing 
a  mineral  acid,  which  is  capable  of  setting  free  nitric  acid  from  the 
nitrate,  to  act  upon  this  salt;  the  nitric  acid  will  act  on  the  sulpho- 
cyanide  as  an  oxidizing  agent;  sulphuric  acid  will  be  formed  at 
the  same  time  as  the  oxidation  is  produced,  but  this  acid  will  liber- 
ate a  fresh  quantity  of  nitric  acid,  which  will  oxidize  more  sulpho- 
cyanide,  while  the  sulphuric  acid  formed  will  be  held  by  the  base 
of  the  sulphocyanide  according  to  the  reaction 

(CNS)  2Ba + 2(N03)  2Ba + S04H2  =  3S04Ba + 2CNH  +  4NO. 

In  this  way  Beringer  claims  that  the  carbonic  acid  formed  at 
the  expense  of  hydrocyanic  acid  is  reduced  to  a  minimum,  and  that 
the  yield  of  this  latter  is  almost  theoretical. 

The  operation  takes  place  in  a  hermetically  closed  receiver 
provided  with  stirrers.  Into  this  receiver  32  kg.  of  barium  nitrate 
and  700  liters  of  water  are  placed  and  the  temperature  brought  to 
the  boiling-point.  Then  are  added  slowly,  either  separately  or 
mixed  together  in  portions  about  equal,  37.2  kg.  barium  sulpho- 
cyanide and  31.6  kg.  sulphuric  acid  of  sp.  gr.  1.84,  to  each  of  which 
100  liters  of  water  have  been  added. 

The  hydrocyanic  acid  liberated  is  carried  away  by  the  watery 
vapor  and  absorbed  in  suitable  receptacles. 

*  Jr.  Soc.  Chem.  Ind.,  1899,  May  31. 


102       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

II.     REDUCTION  PROCESSES. 

The  oxidation  processes  have  never  been  employed  industrially 
to  any  great  extent.  Rauschen's  methods  only  have  enjoyed  some 
interesting  developments.  They  are  in  themselves  rather  danger- 
ous, for  they  all  set  prussic  acid  free,  an  excessively  poisonous  gas. 
Moreover,  there  is  always  fear  of  a  later  oxidations,  the  result  of 
which  would  be  a  greater  or  less  loss  of  cyanogen. 

The  reduction  processes  are  much  more  numerous,  practical,  and 
profitable,  and  at  the  same  time  free  from  danger.  They  are  the 
only  ones  susceptible  of  being  used  in  the  industry  of  the  cyanides 
obtained  by  the  conversion  of  sulphocyanides. 

The  various  substances  proposed  for  the  accomplishment  of 
the  reduction  are  quite  numerous:  Hydrogen,  carbon,  hydro- 
carbons, various  metals,  etc. 

Playfair's  Process. — Playfair  has  thoroughly  investigated  along 
this  line,  and  his  remarkable  researches  have  served  as  a  basis  for 
the  reduction  processes  which  are  used  at  the  present  time. 

In  one  of  his  earlier  investigations  Playfair  attempted  to  heat 
to  redness  a  mixture  of  sulphocyanide  of  sodium  or  of  potassium 
in  a  current  .of  hydrogen,  based  on  the  following  reaction: 

4CNKS  +  6H  =  K2S + 2CNK  +  3H2S + 2C + 2N. 

He  noticed  an  abundant  liberation  of  hydrogen  sulphide;  after 
the  reaction  was  completed  there  remained  in  the  combustion-tube 
a  mixture  of  sulphide  and  cyanide  in  almost  equal  proportions; 
from  his  data,  only  about  80%  of  the  sulphocyanide  was  decom- 
posed. In  the  above  equation,  110  parts  of  potassium  sulphide 
corresponding  to  130  parts  potassium  cyanide,  the  product  of  the 
reaction  yielded  20%  less  cyanide  than  the  theoretical  amount. 
Besides,  one  half  of  the  cyanogen  is  lost,  as  it  is  set  free  in  the  form 
of  nitrogen,  and  the  separation  of  the  cyanide  from  the  sulphide 
is  not  a  very  easy  matter.  This  process  was  therefore  quite  imprac- 
ticable. Several  years  later  Conroy  repeated  Playf air's  experiments 
and  confirmed  every  result. 

Next,  Playfair  tried  the  use  of  hydrocarbon  vapors — naphtha 
vapors  for  example — as  reducing  agent.  As  in  the  preceding  experi- 
ment he  noted  an  abundant  liberation  of  hydrogen  sulphide,  but  at 
the  end  of  the  reaction  he  found  no  traces  of  cyanides.  The  residue 


MANUFACTURE  OF  CYANIDES.  103 

was  composed  entirely  of  sulphides  together  with  slight  traces  of 
formates. 

When  he  heated  sulphocyanide  of  sodium  with  charcoal,  he 
obtained  no  better  results.  In  this  case  he  obtained  traces  only  of 
cyanide  and  a  considerable  quantity  of  sulphide. 

Then  Playfair  tried  the  use  of  metals — at  first  lead  and  zinc,  for 
these  only  appeared  suitable.  The  metals  decomposed  the  sulpho- 
cyanide either  in  fusion  or  in  solution  according  to  the  reaction 

CNKS+R=RS+CNK. 

After  many  experiments,  Playfair  adopted  the  following  pro- 
cedure : 

He  used  a  receiver  made  of  black  lead,  whose  form  is  that  of 
an  inverted  muffle  and  which  is  provided  with  a  tightly  fitting  lid. 
This  apparatus  is  placed  in  a  furnace  in  such  a  way  that  the  top  of 
the  receiver  extends  2  to  5  centimeters  above  the  upper  border  of 
the  furnace  so  that  it  becomes  heated  only  at  the  bottom  and  the 
sides.  Zinc  is  then  melted  in  the  presence  of  a  small  quantity  of 
pulverized  charcoal,  which  maintains  a  reducing  atmosphere  in 
the  crucible.  When  the  zinc  is  completely  fused  dry  sulphocyanide 
is  added,  either  cold  or  even  in  a  melted  state.  The  mass  is  kept 
stirred  and  the  reaction  continued  till  the  mass  becomes  quite  thick 
and  begins  to  redden.  At  this  point  the  reaction  is  complete.  The 
mass  is  then  allowed  to  cool,  protected  from  the  air.  When  cold, 
the  mass  is  easily  removed  from  the  crucible,  which  does  not  appear 
at  all  attacked.  The  color  of  the  mass  should  be  pearly  gray,  if 
the  reaction  has  been  successful,  in  which  case  its  solution  will  be 
entirely  free  of  soluble  sulphides.  But  if  the  mass  has  been  super- 
heated, which  happens  especially  when  too  large  crucibles  are  used, 
it  has  a  brownish  and  sometimes  even  a  reddish  color,  and  the  solu- 
tion may  contain  as  much  as  15%  of  alkaline  sulphide. 

As  a  rule  one  must  assume  a  loss  of  about  5%,  due  partly  to 
moisture  and  partly  to  the  formation  of  small  quantities  of  cyanate 
and  carbonate.  One  should  add  also  to  the  above  loss  that  which 
may  result  from  the  formation  of  the  double  cyanide  of  zinc  and 
potassium  or  sodium  in  consequence  of  a  too  high  temperature,  but 
this  loss  may  be  easily  avoided  by  the  use  of  a  slight  excess  of  sul- 
phocyanide. 


104       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

The  melted  mass  is  subjected  to  a  systematic  lixiviation  in  a 
series  of  vats.  The  alkaline  cyanide  solution  is  separated  from  the 
insoluble  zinc  sulphide  by  decantation.  This  latter  substance  con- 
stitutes about  65%  of  the  fused  mass.  The  solutions  thus  obtained 
vary  considerably  in  concentration;  that  is,  from  4  grams  of  sodium 
cyanide  per  liter  to  220-240  grams.  These  latter  solutions  are 
evaporated  in  vacuum  to  the  consistency  of  a  thick  paste,  which 
on  cooling  crystallize.  The  following  is  an  analysis,  made  by 
Playfair,  of  one  of  these  solutions.  The  figures  represent  the 
amounts  per  100  cc.  of  solution  to  be  evaporated. 

Sodium  cyanide 22.00  gm. 

Cyanate 3.06 

Double  cyanide  of  zinc  and  sodium 1 . 55 

Sodium  carbonate 0. 71 

Sodium  sulphocyanide 1 . 80 

The  following  is  an  analysis,  made  by  Playfair,  of  the  concen- 
trated product : 

Water 26.00% 

Cyanide  of  sodium 54. 70 

Cyanate  of  sodium  (contains  formate) 9.45 

Double  cyanide  of  zinc  and  sodium 3.90 

Sulphocyanide  of  sodium 4 . 30 

Carbonate  of  sodium 1 . 65 

Playf air's  process  marks  a  real  progress;  it  can  be  applied  in- 
dustrially, since,  according  to  the  inventor,  the  yield  is  about  70% 
of  the  theoretical  amount.  This  result  is  obtained  if  care  be  taken 
to  concentrate  the  solutions  in  a  vacuum  of  66  centimeters,  using 
solutions  containing  at  least  22%  of  cyanide,  so  as  to  avoid  loss  of 
cyanogen. 

Dr.  Hans  Luttke's  Process. — This  process  is  based  on  the  same 
principle.  It  consists  in  melting  sulphocyanide  with  zinc  powder. 
In  an  iron  crucible  are  fused  together 

97  kg.  sulphocyanide  of  potassium, 
65  "    zinc  powder. 


MANUFACTURE  OF  CYANIDES.  105 

The  mass  is  stirred  while  being  heated,  and  from  the  moment  it 
fuses,  the  crucible  is  removed  from  the  fire.  The  reaction  then  goes 
on  by  itself. 

When  the  fused  mass  is  treated  with  water  it  yields  about  60  kg, 
of  cyanide,  i.e.,  90%  of  the  theoretical  amount.  The  sulphide  of 
zinc  which  is  obtained  as  a  by-product  may  be  profitably  used  as  a 
mineral  color. 

The  reaction  takes  place  between  360°  and  400°;  this  temperature 
may  be  lowered  by  an  addition  of  1%  to  2%  caustic  alkali,  which 
at  the  same  time,  increases  the  yield  of  cyanide. 

Various  other  metals  have  been  tried.  Lead,  which  was  also 
recommended  by  Playfair,  has  the  advantage  of  not  forming  double 
cyanide  of  lead  and  potassium,  but  on  account  of  its  high  atomic 
weight,  three  times  as  much  lead  as  zinc  are  required  to  perform 
the  same  work,  while,  at  the  same  time,  it  has  a  tendency  of  falling 
to  the  bottom  of  the  crucible  without  remaining  mixed  with  the 
sulphocyanide. 

The  reduction  of  sulphocyanide  may  be  well  carried  on  with  the 
use  of  tin,  but  tin  sulphide  dissolves  in  rather  appreciable  quanti- 
ties in  the  alkaline  cyanide. 

The  use  of  copper  is  no  more  successful,  for  it  gives  rise  to  cupro- 
cyanides. 

Process  of  the  British  Cyanide  Company. — Notwithstanding  the 
foregoing,  this  company  has  quite  recently  patented  a  process  in 
which  copper  is  used.  This  process  is  based  on  the  fact  that  when 
metallic  cyanide  compounds  are  heated  in  a  current  of  hydrogen  at 
a  suitable  temperature,  they  set  free  the  whole  of  their  cyanogen  in 
the  form  of  hydrocyanic  acid,  which  may  be  absorbed  by  alkaline 
solutions.  The  British  Cyanides  Company,  Limited,  noticed  that  the 
salt  which  is  the  best  adapted  for  this  reaction  is  sulphocyanide  of 
copper.  This  salt,  which  is  first  thoroughly  dried,  is  placed  in  a 
receiver  provided  with  a  stirrer  and  mixed  with  finely  divided  copper 
in  considerable  excess  (equal  quantities  of  sulphocyanide  and  of 
copper).  Perfectly  dry  hydrogen  is  passed  through  the  apparatus, 
in  order  to  expel  the  air  and  then  it  is  heated  to  150°  C.,  and  grad- 
ually to  350°  C. 

When  the  reaction  is  almost  complete,  the  temperature  is  raised 


106       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

to  500°  C.;  the  current  of  hydrogen  being  constantly  kept,  up.    The 
reaction  is  as  follows: 

(CNS)  2Cu2 + 2Cu + H2  =  2Cu2S  +  2CNH. 

The  gas  which  is  liberated  is  a  mixture  of  hydrocyanic  acid  with 
hydrogen  in  excess.  It  is  conducted  through  a  strong  alkaline 
solution  which  absorbs  the  hydrocyanic  acid.  The  excess  of  hydro- 
gen may  then  be  collected  and  used  anew.  The  cuprous  sulphide 
remaining  behind  may  be  treated  in  order  to  recover  the  copper 
or  copper  salts.  In  place  of  hydrogen  may  be  used  coal-gas  or 
water-gas  provided  they  be  free  from  carbonic  acid,  oxygen,  and 
moisture. 

Conroy  tried  using  copper  and  zinc  simultaneously,  or  copper 
with  lead-sodium  alloy,  but  in  neither  case  was  he  able  to  obtain 
a  pure  product. 

The  results  obtained  with  iron  were  quite  satisfactory.  In  his 
patent,  No.  21,451,  obtained  in  1893,  Conroy  recommends  treating 
the  dry  sulp  ocyanide  with  finely  divided  reduced  iron,  pitch,  and 
a,  small  amount  of  charcoal  in  order  to  prevent  oxidation.  The 
reaction  takes  place  at  about  400°,  but,  as  Conroy  himself  noticed 
it  is  quite  irregular,  and  the  yield  may  be,  in  consequence,  quite 
variable.  Moreover,  it  is  rather  difficult  to  ascertain  exactly  the 
end  of  the  reaction,  and  if  the  operation  be  carried  on  too  far,  reac- 
tions may  take  place  which  are  quite  opposed  to  those  desired. 

Hetherington  and  Musspratt's  Process. — This  process  (English 
patent  5830,  1894)  is  based  on  this  principle:  It  consists  in  heat- 
ing iron  filings  or  turnings  with  tar  in  order  to  reduce  the  oxide 
coating  to  the  metallic  state.  The  iron  thus  treated  is  mixed  in 
the  proportion  of  70  to  80  parts  with  20  to  40  parts  tar  and  100 
parts  alkaline  sulphocyanide.  This  mixture  is  heated  to  350°  C., 
thereabouts,  in  a  closed  vessel  connected  by  means  of  a  tube  with 
a  retort,  where  the  volatilized  sulphocyanide  is  condensed.  The 
resulting  product  is  iron  sulphide,  a  tar-like  residue,  and  alkaline 
ferrocyanide.  It  is  treated  with  hot  water,  and  the  filtered  solu- 
tion is  subjected  to  the  action  of  a  current  of  carbonic  acid,  which 
displaces  the  hydrogen  sulphide,  after  which  the  solution  is  con- 
centrated to  crystallization. 


MANUFACTURE   OF  CYANIDES.  107 

Process  of  the  Silesia  Verein  Chemische  Fabrik. — This  process  is 
in  all  points  about  the  same  as  the  foregoing.  The  sulphocyanide 
is  first  melted,  then  poured  upon  reduced  iron  filings,  turnings,  or 
shavings,  and  then  heated  to  dull  redness.  For  this  purpose  1  kg. 
of  iron  may  be  profitably  used  for  each  kilogram  of  crystallized 
sulphocyanide. 

If  the  sulphocyanide  be  in  solution,  this  is  concentrated,  and 
iron  shavings  added  in  sufficient  quantity  to  form  a  pasty  mass. 
This  is  then  transferred  to  receivers  of  moderate  dimensions 
which  can  be  transported  and  heated  at  a  temperature  not  above 
800°.  In  order  to  complete  the  decomposition  properly,  incan- 
descent bodies,  such  as  pieces  of  iron,  charcoal,  and  highly  heated 
stones,  are  thrown  on  the  mass.  Then  the  receiver  is  removed  from 
the  fire  and  allowed  to  cool. 

In  each  case  the  product  is  treated  either  with  water,  in  order 
to  obtain  ferrocyanide,  or  with  alcohol,  in  order  to  obtain  cyanide. 

Goerlich  and  Wichmann's  Process. — This  process  differs  but 
little.  It  consists  in  fusing  the  sulphocyanide  with  iron,  passing 
a  moist  current  of  air  charged  with  carbonic  acid  through  the  fused 
mass  and  then  treating  it  with  water  according  to  the  reaction 

2K6Cy6  •  6FeS  4- 170  +  21H20  +  2C02 

=  2K4FeCy6  •  3H20  +  2C08K2  +  5Fe2(OH)  6  +  2S 

At  the  present  time  the  transformation  of  sulphocyanides  into 
cyanides  is  preferably  done  in  the  wet  way. 

These  processes  originated  with  the  patents  taken  out  by  Pitt 
and  Bower,  the  object  of  which  was  the  recovery  of  the  cyanide 
compounds  occurring  in  gas-liquor. 

Bower's  Process. — In  Bower's  first  process  these  gas-liquors  are 
treated  with  addition  of  metallic  iron  or  ferric  salt  in  sufficient 
quantity  to  convert  the  whole  of  the  cyanide  compounds  into  ferro- 
cyanide and  iron  sulphocyanide.  After  distilling  off  the  ammonia 
in  the  presence  of  lime,  the  residual  liquors  containing  the  sulpho- 
cyanide and  ferrocyanide  of  calcium  are  treated  with  an  acid  solu- 
tion of  cuprous  chloride,  which  precipitates  the  cyanide  compounds 
as  insoluble  cuprous  salt.  While  this  precipitate  is  still  moist,  it 
is  treated  with  finely  divided  iron  in  order  to  convert  it  into  soluble 


108       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

iron  sulphocyanide  and  insoluble  iron  ferrocyanide.  At  the  same 
time  metallic  copper  is  formed.  The  ferrocyanide  of  iron,  which 
is  separated  by  filtration,  is  treated  with  a  strong  alkaline  solu- 
tion in  order  to  obtain  an  alkali  ferrocyanide.  The  solution  of  iron 
sulphocyanide  is  evaporated. 

Later  Bower  noted  that  when  the  decomposition  of  copper 
sulphocyanide  is  brought  about  by  the  use  of  iron  at  a  high  tem- 
perature and  under  pressure,  the  copper  which  is  set  free  reacts 
with  the  sulphur  of  the  iron  sulphocyanide  and  forms  copper  sul- 
phide and  iron  ferrocyanide.  Bower  immediately  obtained  a  new 
patent,  according  to  which  the  iron  sulphocyanide  obtained  as 
before  stated  is  treated  with  metallic  copper  in  an  autoclave  and 
at  a  high  temperature  under  pressure. 

The  reaction  follows: 

3(CNS)  2Fe + 6Cu  =  Fe(CN)  2  •  2Fe(CN)  2 + 6CuS. 

The  precipitate  obtained  is  afterward  treated  with  an  alkaline  or 
alkaline-earth  solution  giving  a  soluble  ferrocyanide. 

Conroy's  Process. — Taking  up  Bower's  work,  Conroy  thought  of 
substituting  another  and  less  expensive  metal  for  copper,  and  chose 
iron.  He  noted  that  if  a  solution  of  iron  sulphocyanide  be  boiled 
under  pressure  with  metallic  iron  there  will  be  formed  at 

Undecomposed        F  |de 


Iron 
Sulphocyanide. 


Obtained. 


115°-125°  (after  heating  13  hours). 62.0%  36.8% 

150°-165°      "         "         4     "      10.6%  88.0% 

190°-200°  .   "         "         2J  "      9.2%  90.5% 

Having  settled  this  important  point,  Conroy  sought  to  obtain 
a  similar  result  with  potassium  sulphocyanide  or  other  impure 
sulphocyanide. 

His  first  experiment  along  this  line  was  with  a  mixture  of 
potassium  sulphocyanide  with  a  soluble  iron  salt.  The  results  were 
as  follows: 

Non-decomposed        Ferrocyanide 
Sulphocyanide.  Obtained. 

At  160°  with  1  hour's  heating 38.0%          52.  6% 

At  160°    "    2  hours'       "     22.0%          67.5% 

At  150°-160°  with  5J  hours'  heating —  95.0% 


MANUFACTURE  OF  CYANIDES.  109 

The  result  being  favorable,'  Conroy  determined  to  apply  this 
method  on  an  industrial  scale,  and  in  order  to  do  this  he  undertook, 
in  company  with  Hawliczek  and  Clayton,  experiments  bearing  upon 
calcium  sulphocyanide,  the  important  industrial  waste  product  in 
the,  manufacture  of  gas. 

In  a  cast-iron  cylindrical  autoclave  provided  with  a  stirrer  turn- 
ing at  the  rate  of  40  revolutions  per  minute  a  mixture  of  (1)  a  solu- 
tion of  calcium  sulphocyanide,  400  g.  per  liter;  (2)  a  solution  of 
ferrous  chloride,  250  gm.  per  liter  and  an  excess  of  iron  filings  or 
shavings  is  heated  to  135°-140°  C.  and  under  a  pressure  of  50-60 
pounds  per  square  inch.  Under  these  conditions  he  observed  that 
the  time  of  the  decomposition  of  the  sulphocyanide  that  it  varies 
with  the  amount  and  fineness  of  the  iron  used,  according  to  the 
following  table 

Iron  in  Excess  of  Sulphocyanide  Time  of 

Theoretical  Amt.  Decomposed.  Reaction. 

12   hours 

Si     " 

Si     ". 

According  to  Conroy  the  reaction  is  as  follows: 

2CNSK+FeCl2+2Fe  =  2KCl+Fe(CN)2+2FeS. 

The  mixture  of  sulphide  and  of  ferrocyanide  of  iron  is  then 
treated  with  a  strong  alkaline  solution,  there  being  formed  soluble 
alkali  ferrocyanide,  while  the  sulphide  of  iron  undecomposed  re- 
mains insoluble: 

3(CN)2Fe+4KOH+H20  +  0  =  Fe(CN)6K4+Fe2(OH)6. 

But  this  treatment  requires  a  large  excess  of  alkali,  and  moreover 
there  is  an  appreciable  loss  of  this  compound  varying  from  12%-28%. 
It  is  better  to  replace  it  by  treatment  with  hydrochloric  acid.  In 
fact,  if  the  mixture  be  treated  with  this  acid  the  sulphide  of  iron 
goes  into  solution,  while  a  pale-blue  precipitate  is  formed  which  is 
insoluble  in  hot  potassium  carbonate,  but  which  yields  potassium 
ferrocyanide  under  the  action  of  a  current  of  air. 

This  method  presents,  moreover,  the  great  advantage  of  giving 
ferrous  chloride,  which  may  thus  be  used  in  the  reaction 

3(CN)2Fe+6KCl+FeS  =  Fe(CN)6K4+3FeCl2+K2S. 


Iron  shavings  
Reduced  iron  

8        times 
J5.55     " 
[1.70     " 

92.5% 
94-0% 
85-99 

110      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

All  these  processes  yield  ferrocyanide,  which  product  must  then 
be  reduced  to  cyanide.  They  therefore  do  not  solve  the  problem 
completely,  which  is  the  production  of  the  cyanide  direct. 

Raschen,  Davidson,  and  Brock's  Process.  —  Nevertheless  there 
exist  special  processes  which  fulfill  this  purpose,  among  them  may 
be  cited  that  of  Raschen,  Davidson,  and  Brock  (1894).  It  is  based 
on  the  conversion  of  sulphocyanides  into  cyanides  by  ignition  in  the 
presence  of  an  excess  of  alkali  or  of  alkaline  earth,  together  with 
charcoal  or  a  hydrocarbon.  The  sulphocyanide  used  in  this  case 
is  produced  by  the  action  of  carbonic  acid  on  a  mixture  of  milk  of 
lime,  sulphide  of  carbon,  and  ammonia  heated  in  a  closed  vessel. 
The  resulting  product  is  treated  with  an  alkaline  carbonate  filtered 
and  evaporated  to  dryness.  Quicklime  is  added  to  the  crude  sulpho- 
cyanide together  with  a  mixture  of  powdered  charcoal,  resin,  tar, 
or  any  other  such  substance.  The  whole  mass  is  heated  as  rapidly 
as  possible  to  a  bright-redness  in  a  vessel  provided  with  a 
stirrer. 

The  mass  is  then  allowed  to  cool,  avoiding  as  far  as  possible  the 
access  of  air,  and  then  it  is  washed  with  water.  In  this  way  is 
obtained  a  solution  of  alkali  cyanide  containing  a  small  amount  of 
calcium  sulphide,  which  latter  product  may  be  gotten  rid  of  by  well- 
known  methods. 

Theoretically,  this  process  seems  very  simple  and  reasonable, 
but  unfortunately  no  data  could  be  obtained  concerning  the  yields 
which  it  furnishes  and  concerning  its  industrial  application. 

Etard's  Process. — This  process,  which  has  already  been  mentioned 
(Chapter  I,  §  1)  and  which  consists  in  treating  the  alkali  sulpho- 
cyanide with  the  ferrocryanide  of  the  same  metal  either  alone  or 
mixed  with  a  carbonate,  has  not,  to  our  knowledge,  been  industri- 
ally applied. 

Finlay's  Process. — Finally  may  be  mentioned  the  original  process, 
patented  in  Germany  by  Finlay  (patent  8604,  1896).  It  consists 
in  producing  simultaneously  sulphocyanide  and  alkali  cyanide 
by  igniting  at  1000°  a  mixture  of  alkali  or  of  alkaline  earth  with 
charcoal  in  an  atmosphere  free  from  oxygen  and  consisting  chiefly 
of  nitrogen  and  sulphuric  anhydride.  Through  the  solution  of  the 
mixture  thus  produced  a  current  of  nitrogen  and  carbonic  acid,  in 
the  presence  of  an  oxidizing  agent,  is  passed.  Hydrocyanic  acid 


MANUFACTURE  OF  CYANIDES.  Ill 

is  removed  and  passes  into  an  alkaline  solution,  forming  an  alkali 
cyanide. 

Finlay  recommends  the  following: 

A  mixture  of  equal  parts  of  charcoal  and  caustic  or  carbonated 
alkali,  especially  barium  carbonate,  is  heated  to  about  1000°.  A 
mixture  of  nitrogen  and  sulphur  dioxide  obtained  by  direct  com- 
bustion of  sulphur  in  air  is  transmitted  upon  the  incandescent  mass. 
Under  these  conditions  there  is  produced  a  mixture  of  cyanide  and 
sulphocyanide  of  barium.  When  this  reaction  is  complete,  the  mass 
is  allowed  to  cool  and  is  taken  up  with  water.  After  a  suitable 
addition  of  an  oxidizing  agent  (of  the  nature  and  use  of  which  Finlay 
gives  no  information)  a  mixture  of  nitrogen  and  carbonic  acid  ob- 
tained by  the  combustion  of  charcoal  in  a  current  of  air  is  trans- 
mitted into  this  boiling  solution.  The  barium  separates  out  as  an 
insoluble  carbonate,  while  the  hydrocyanic  acid  which  is  displaced 
is  carried  off  by  the  gaseous  current.  The  hydrocyanic  acid  is  con- 
densed in  a  cooler  kept  at  a  temperature  of  4°-5°  C.  and  combined 
with  a  caustic  alkali.  At  the  same  time  the  sulphocyanide  is  de- 
composed into  hydrocyanic  acid  and  sulphur  dioxide.  This  latter, 
carried  off  by  the  nitrogen,  regenerates  thus  the  initial  mixture  of 
gas  used  for  the  production  of  cyanide  and  sulphocyanide. 

On  account  of  its  originality,  this  process  deserves  some  atten- 
tion, but  unfortunately  it  is  quite  probable  that  the  liberation  of 
hydrocyanic  acid  will  check  its  industrial  development,  as  is  the 
case  in  all  those  processes  where  such  a  liberation  takes  place. 

II.   SYNTHETIC  PROCESSES. 
GENERAL  REMARKS. 

It  is  the  custom  to  designate  under  "  synthetic  or  direct  proc- 
esses/' all  those  processes  the  essential  principle  of  which  consists 
in  uniting  by  means  of  any  energy  the  three  fundamental  bodies 
entering  into  the  composition  of  cyanides — carbon,  nitrogen,  and 
alkali  metal — these  three  bodies  capable  of  being  either  in  a  free  or 
nascent  state  or  in  a  combined  state. 

The.  indirect  processes  which  have  just  been  reviewed  have  been 
able  to  supply  the  needs  of  the  trade  at  a  time  when  the  use  of  cya- 
nides was  very  limited,  but  soon  the  requirements  of  industry  made 
necessary  simpler,  less  defective,  and  less  expensive  processes. 


112       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

Nitrogenous  organic  substances,  which  for  a  long  time  have 
been  the  raw  materials  of  this  industry,  have  in  general  a  very  high 
value  relatively,  because  of  their  extensive  use  either  in  human 
or  animal  nutrition,  or  in  agriculture,  or  in  other  industries.  There- 
fore they  could  not  be  economically  used  for  a  preparation  which 
utilizes  only  their  carbon  and  nitrogen. 

It  is  consequently  necessary,  if  it  is  desired  to  work  under  really 
economic  conditions,  to  make  use  of  waste  or  refuse  products,  which 
are  necessarily  insufficient,  especially  from  the  point  of  view  of 
the  percentage  of  useful  products  which  they  contain. 

The  percentage  of  nitrogen  in  these  substances  is  especially 
small  in  comparison  with  that  of  carbon;  therefore  it  is  always 
necessary  to  ignite  them  beforehand,  in  order  to  obtain  a  much 
richer  nitrogenous  charcoal.  In  this  preliminary  operation  f 
of  the  nitrogen  is  lost  under  the  form  of  ammonia.  This  loss  is 
unfortunately  not  the  only  one,  and  at  the  time  of  the  forming  of 
the  cyanide  with  the  nitrogenous  charcoal  f  and  even  f-  of  that 
remaining  is  lost,  so  that  finally  only  J  or  ^  of  the  total  nitrogen 
is  utilized. 

If  to  these  losses  in  nitrogen  be  added  those  not  less  important, 
occasioned  by  poor  yield,  from  the  point  of  view  of  the  alkali  car- 
bonate used,  and  those  produced  by  the  volatilization  of  the  cyanide 
at  the  temperature  at  which  it  is  necessary  to  work,  it  is  easy  to 
see  that  such  processes  are  far  from  giving  satisfactory  results  or 
being  economical,  notwithstanding  the  remarkable  improvements 
which  they  have  undergone. 

It  is  therefore  quite  natural  to  have  sought  to  produce  cyanides 
by  the  synthetic  or  direct  way,  which,  besides  the  advantage  it 
possesses  of  producing  the  product  desired  directly,  allows  this 
product  to  be  obtained  much  cheaper  and  in  a  state  of  greater 
purity.  Of  the  three  substances  which,  in  general,  constitute  the 
cyanides,  carbon  occurs  wide-spread,  is  easily  found,  and  very  cheap ; 
the  alkali  metals  are  likewise  widely  distributed.  As  to  the  nitro- 
gen, although  it  occurs  distributed  in  extensive  amounts  on  the 
surface  of  the  globe,  it  is  quite  difficult  to  produce  in  a  free  state. 

Constituting  four  fifths  of  the  atmosphere  which  surrounds  us,  it  is 
quite  natural  to  think  of  utilizing  the  nitrogen,  either  in  the  form 
of  air  or  in  the  free  state  extracted  from  the  air.  The  idea  of  using 


MANUFACTURE   OF  CYANIDES.  113 

the  atmospheric  air  in  the  manufacture  of  cyanides  is  not  new. 
It  proceeds  from  a  series  of  observations  made  by  many  investi- 
gators. 

In  1828  a  chemist  of  Besanon,  named  Desfosses,  repeating 
the  old  experiments  of  Scheele  and  Curandeau,  remarked  that  the 
nitrogen  unites  with  carbon  in  order  to  form  cyanogen  when  a 
current  of  this  gas  or  of  air  passes  over  a  mixture  of  charcoal  and 
carbonate  of  potash  at  a  red  heat. 

In  1835  Dawes  discovered  the  existence  of  cyanide  of  potassium 
in  the  molten  masses  which  are  formed  in  the  furnaces  for  the  smelt- 
ing of  iron. 

In  1837  the  English  investigator  Clark  made  the  same  discovery. 
In  examining  an  efflorescence  which  was  produced  at  the  orifice  of 
some  blast-furnaces  on  the  Clyde,  he  noticed  that  it  was  made  up 
almost  entirely  of  potassium  cyanide. 

In  the  same  year,  having  established  hot-air  bellows  in  blast- 
furnaces, Neilson  likewise  observed  the  formation  of  masses  which 
contained  up  to  43%  potassium  cyanide. 

These  were  confirmed  by  other  observations,  notably  in  the 
Harz,  at  Magdesprung,  and  at  Zuicken  by  Bromeis  in  1842.  In 
1843  Redtenbacher  proved  a  similar  phenomenon  in  the  furnaces 
at  Mariazell  in  Styria,  where  the  production  of  potassium  cyanide 
thereby  became  industrially  important. 

Moreover,  in  1839  Lewis  Thompson  demonstrated  that  if  a 
mixture  of  coke,  potassium  carbonate,  and  iron  filings  be  heated 
at  a  high  temperature  and  a  current  of  air  be  passed  over  the  mass, 
there  will  be  formed  potassium  cyanide  the  yield  of  which  will  be 
greater  than  that  obtained  by  not  using  air  even  when  animal 
charcoal  rich  in  nitrogen  be  used.  On  account  of  this  remarkable 
investigation  the  Society  of  Arts  bestowed  a  gold  medal  on  Lewis 
Thompson. 

In  1841  Fowner,  and  likewise  Young,  confirmed  this  result. 

But  other  chemists,  and  particularly  Erdmann  and  Marchand  in 
1841,  and  Wohler  somewhat  later,  disputed  their  assertions,  and 
claimed  that  the  cyanide  formed  was  due  entirely  to  the  nitrogen 
of  the  coal  and  that  the  reaction  would  not  take  place  with  dry 
substances. 

In  1845  the  question  of  the  formation  of  cyanide  in  the  blast- 


114       METHODS   OF  MANUFACTURING  CYANIDE   COMPOUNDS. 

furnaces  being  studied  more  thoroughly,  Bunsen  and  Playfair  were 
able  to  show  that  this  product  is  formed  in  the  zone  situated  exactly 
above  the  blast-pipes  through  which  hot  air  was  being  blown.  They 
experimented  on  this  subject  with  the  result  that  it  received  scien- 
tific and  industrial  sanction  and  exerted  a  considerable  influence 
on  the  ideas  concerning  the  role  played  by  nitrogen.  By  making 
an  opening  in  the  wall  of  a  blast-furnace  of  the  iron- works  at  Alfreton, 
exactly  above  the  orifice  of  the  blast-pipes,  they  noted  the  formation 
of  an  abundant  sublimation  of  potassium  cyanide,  which,  according 
to  their  calculation,  might  react  188  kg.  in  24  hours.  From  this 
experiment  they  drew  the  conclusion  that  the  cyanide  formed  was 
due  solely  to  the  atmospheric  nitrogen,  and  not  to  that  chemically 
combined  with  the  coal.  Moreover,  they  established  clearly  the  proba- 
bility of  this  theory  by  another  experiment. 

In  passing  air  through  a  tube  containnig  a  mixture  of  1  part 
sugar  charcoal  and  2  parts  of  perfectly  pure  carbonate  of  potash, 
heated  to  a  temperature  high  enough  to  cause  the  reduction  of  the 
alkali  carbonate,  they  obtained  an  abundant  formation  of  potassium 
cyanide. 

In  1851  Riecken  confirmed  in  all  points  the  data  presented 
by  Bunsen.  This  investigator  showed  without  any  doubt  that 
cyanogen  may  be  formed  in  the  absence  of  every  other  source  of 
nitrogen  except  that  of  atmospheric  air,  provided  that  the  latter  be 
previously  heated  and  transmitted  in  the  form  of  a  continuous  current, 
and  that  the  reaction  be  carried  on  at  a  temperature  sufficiently 
high  to  reduce  the  potassium  compounds  employed  to  the  metallic 
state. 

Some  time  later  Delbruck's  new  experiments  removed  all  doubt 
from  the  works  of  Bunsen  and  Riecken. 

These  first  principles  being  admitted,  it  was  immediately  planned 
to  make  it  the  basis  of  a  process  for  the  manufacture  of  cyanide  on 
an  industrial  scale. 

The  first  practical  application  undertaken  along  this  line  was 
in  1843.  This  was  made  by  Possoz  and  Boissiere,  at  first  in 
their  works  at  Grenelle,  and  the  next  year  at  Newcastle,  under  the 
direction  of  an  English  company.  This  process  was  based  on  the 
fact  demonstrated  by  Desfosses  in  1841,  that  if  a  current  of  nitrogen 
be  passed  over  a  mixture  of  charcoal  and  potassium  carbonate 


MANUFACTURE  OF  CYANIDES.  115 

heated  to  redness,  there  is  formation  of  potassium  cyanide.  Not- 
withstanding unheard-of  efforts,  great  sacrifices,  and  several  years 
of  struggle  and  in  spite  of  their  rare  perseverance,  the  two 
French  chemists  could  not  hold  out  against  competition,  and  were 
forced  to  abandon  the  exploitation  of  their  process.  That  was 
because  the  yield  of  cyanide  was  small,  and  consequently  the  net 
cost  was  greatly  increased. 

Numerous  attempts  followed  that  of  Possoz  and  Boissiere,  and 
among  them  may  be  c  ted : 

In  England,  those  of  Newton  in  1843,  Swindel  in  1844,  Blairs 
and  Bromwell  in  1847. 

In  Germany,  those  of  Welden  in  1879,  and  Alder  in  1881. 

In  America,  those  of  Mond  in  1882,  Fogarty  in  1883  and  1887, 
and  Dickson  in  1887. 

And,  finally,  in  France,  those  of  Ertel  in  1846,  Armengaud  in 
1847,  and  Margueritte  and  Sourdeval  in  1862. 

All  these  processes  are  based  on  the  action  of  atmospheric  air 
on  a  mixture  of  charcoal  and  an  oxide  or  carbonate  of  an  alkali 
heated  to  a  very  high  temperature. 

The  results  obtained  by  these  various  manufacturers,  however 
encouraging  they  may  have  been,  were  nevertheless  far  from  being 
satisfactory.  Therefore  these  processes  had  a  very  short  existence. 

The  quantities  of  cyanides  produced  were,  in  fact,  very  small, 
and  the  net  cost  was  consequently  very  great.  If  to  this  great 
objection  be  added  that  none  the  less  serious  of  the  rapid  wear  and 
tear  of  apparatus  brought  about  by  the  extremely  high  temperature 
necessary  for  producing  the  reaction,  the  causes  of  the  failure  of 
these  attempts  will  be  readily  understood. 

The  attempt  was  made  to  overcome  the  difficulty  by  utilizing 
nitrogen  in  another  form,  and  for  this  purpose  ammonia-gas  was 
suggested.  This  gas  in  fact,  besides  being  relatively  cheap,  is 
14/i7  of  its  weight  in  the  form  of  nitrogen,  and  it  has  a  greater  chem- 
ical affinity  than  that  of  nitrogen.  In  fact  it  was  proved  by  the 
experiments  of  Langlois  and  Kuhlmann  that  if  dry  ammonia- 
gas  be  passed  over  charcoal  heated  to  redness  there  will  be  formed 
ammonium  cyanide  according  to  the  reaction 

4NH3 + 3C  =  2NH4  •  CN  +  CH4. 


116       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

This  was  not,  indeed,  a  new  idea.  Brunnquell,  later  Karmrodt, 
and  finally  Lucas  had  already  tried  to  utilize  the  ammonia  produced 
in  the  ignition  of  nitrogenous  organic  matters,  and  which  forms 
part  of  the  volatile  products  arising  from  this  decomposition. 
Toward  this  end  these  products  were  made  to  pass  through  retorts 
or  cylinders  charged  with  charcoal  impregnated  with  potash;  but 
notwithstanding  certain  advantages  these  processes  never  received 
industrial  sanction. 

Laming,  in  1843  and  1845,  made  this  idea  the  basis  of  two  processes 
for  the  manufacture  of  cyanides.  But  these  attempts  were  like- 
wise futile.  Other  manufacturers  and  investigators  studied-  this 
question  also,  their  results  often  being  contradictory  and  their  experi- 
ments were  never  taken  up  outside  the  laboratory. 

The  weak  points  of  the  experiments  undertaken  along  this  line 
are  (1)  the  difficulty  of  manipulating  such  a  volatile  gas  as  am- 
monia, (2)  the  necessity  of  producing  a  very  high  temperature, 
(3)  the  considerable  loss  due  to  volatilization,  and  (4)  the  rapid 
deterioration  of  the  apparatus. 

To  the  above  should  likewise  be  added  the  fact  that  at  such 
high  temperatures  ammonia-gas  begins  to  undergo  an  appreciable 
decomposition,  which,  of  course,  is  lost  to  the  reaction. 

Another  very  ingenious  solution  of  the  problem  had  been  pro- 
posed by  Gelis,  and  was  taken  up  about  25  years  ago  by  Tcherniac 
and  Gunzburg.  It  consisted  in  producing  cyanides  through  the 
intermediary  of  sulphocyanides,  formed  by  the  action  of  ammonia 
on  the  sulphide  of  carbon. 

During  the  last  few  years  this  question  has  again  become  the 
object  of  numerous  and  important  researches,  but  along  other  lines, 
and  which  permits  the  discovery  of  a  real  synthetic  process  to  be 
foreseen  in  the  near  future,  a  process  at  once  practical  and  of  in- 
dustrial value. 

These  processes  are  based  on  the  action  of  nitrogen  or  of  am- 
monia upon  the  alkali  metals  or  their  carbides. 

The  reaction  of  ammonia  oh  the  alkali  metals  was  shown  a  long 
while  ago  by  Gay-Lussac  and  Thenard. 

It  is,  in  fact,  known  that  if  perfectly  dry  ammonia-gas  be  passed 
over  potassium  or  sodium  at  a  suitable  temperature  (not  very  high) 
a  clearly  defined  compound,  an  alkali  amide,  is  obtained  which  in 


MANUFACTURE  OF  CYANIDES.  117 

contact  with  charcoal  under  suitable  condition  forms  alkali  cyanide. 
The  low  price  and  the  facility  with  which  large  quantities  of  alkali 
metals  are  prepared  leads  to  the  belief  that  processes  based  upon 
this  reaction  will  be  put  to  practical  use.  It  is  evident  that  in  this 
case  it  is  no  longer  necessary  to  produce  the  extreme  temperature 
required  for  the  reaction  of  alkaline  compounds  formerly  used,  and 
from  this  fact  losses  through  volatilization  will  be  avoided  while 
decreasing  the  wear  and  tear  of  the  apparatus. 

On  the  other  hand,  it  is  to-day  clearly  proven  that  carbides  are 
capable  of  fixing  nitrogen,  and,  under  certain  conditions,  of  forming 
cyanides. 

These  two  important  observations  have  formed  the  basis  of 
numerous  patents  recently  granted,  especially  in  Germany.  The 
experiments  seem  to  be  successful,  and  in  the  near  future  the  solu- 
tion of  this  question  may  be  met. 

The  solution  would  all  the  more  be  hastened  through  the  dis- 
covery of  a  practical  and  economical  process  of  fixing  the  nitrogen 
of  the  air,  a  question  which  has  likewise  made  considerable  progress, 
and  all  the  more  through  the  synthetic  production  of  ammonia  by 
the  aid  of  this  same  nitrogen. 

Whenever  this  problem  is  solved,  that  of  the  manufacture  of 
cyanides  will  be  near  its  solution. 

The  synthetic  processes  put  into  operation  may  be  divided  into 
two  large  classes: 

(1)  Processes  using  atmospheric  nitrogen. 

(2)  Processes  using  ammoniacal  nitrogen. 

Some  of  these  processes  are  capable  of  using  either  atmospheric 
nitrogen  or  the  nitrogen  of  ammonia.  Such  processes  will  only  be 
mentioned  in  the  first  class,  but  will  be  discussed  among  those 
processes  which  are  based  on  the  use  of  ammonia. 


A.     PROCESSES  USING  ATMOSPHERIC  NITROGEN. 

The  discovery  of  potassium  cyanide  in  blast-furnaces,  and  the 
remarkable  investigations  of  Bunsen,  Playfair,  Riecken,  and  of  Del- 
bruck,  which  fixed  in  an  irrefutable  manner  the  remarkable  role 
played  by  atmospheric  nitrogen  in  this  formation,  had  the  happy 


118       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

result  of  inciting  manufacturers  and  investigators  to  utilize  atmos- 
pheric air,  or  the  nitrogen  contained  therein  for  the  manufacture  of 
cyanide  compounds. 

As  is  well  known,  the  atmosphere  is  composed  of  a  mixture  of 
oxygen  and  nitrogen,  contaminated  more  or  less,  according  to 
circumstances,  with  water,  carbonic  acid,  ammonia,  etc.  In  reality 
nitrogen  forms  about  four  fifths  of  the  air,  since  air  is  composed  of 
21%  oxygen  and  79%  nitrogen  by  volume,  or  23%  and  77%  by 
weight.  Air  therefore  is  an  inexhaustible  and  profitable  source 
of  nitrogen  for  the  manufacture  of  cyanides. 

At  first  it  was  attempted  to  use  the  atmospheric  air,  but  the 
presence  of  the  oxygen  interfered  considerably  with  the  reactions. 
That  is  the  reason  why  the  attempt  was  made  to  use  the  nitrogen 
from  which  the  oxygen  had  previously  been  removed. 

The  separation  o£  these  two  gases  is  not  such  an  easy  task  as  one 
would  be  led  to  believe,  and  several  methods  have  been  devised  for 
this  purpose.  Therefore  it  may  not  be  out  of  place,  before  taking 
up  the  study  of  processes  for  the  manufacture  of  cyanides  by  the 
use  of  nitrogen  of  the  air,  to  first  pass  in  review  the  various  means 
employed  for  the  separation  of  these  two  principal  constituents  of 
air,  oxygen,  and  nitrogen. 

These  methods  almost  all  depend  on  the  following  principle: 
If  a  current  of  air  be  passed  over  an  easily  oxidizable  substance 
tinder  suitable  conditions,  this  substance  will  absorb  the  oxygen 
and  leave  the  nitrogen  free  and  pure. 

Most  oi  the  metals,  and  even  certain  metalloids — e.g.,  phosphorus 
or  charcoal — may  be  used  for  this  purpose. 

As  a  rule,  whenever  it  is  desired  to  obtain  almost  chemically  pure 
nitrogen,  copper  or  iron  is  used. 

A  current  of  air  is  passed  over  copper  heated  to  redness,  which 
absorbs  the  oxygen  with  formation  of  oxide  of  copper,  while  the 
nitrogen  is  left  almost  pure.  Often  passing  the  gas  only  once 
over  the  metal  is  not  enough  for  the  total  absorption  of  the 
oxygen.  This  is  an  objection  which  may  be  easily  .remedied,  and 
thus  a  gas  absolutely  free  from  oxygen  obtained.  This  operation 
being  carried  on  at  a  high  temperature,  the  resulting  gases  are  like- 
wise hot,  which  fact  may  be  of  great  use  in  certain  processes. 

Lupton  has  modified  this  pr  cess  in  such  a  way  that  a  better 


MANUFACTURE  OF  CYANIDES.  119 

yield  of  nitrogen  is  obtained,  and  the  process  is  carried  on  con- 
tinuously. 

His  process  consists  in  passing  air  through  an  aqueous  solution 
of  ammonia  before  passing  it  over  the  copper;  the  ammonia  carried 
away  by  displacement  then  passes  over  the  oxide  of  copper  formed 
and  reduces  it  to  metallic  copper  according  to  the  reaction 
3CuO+2NH3  =  3Cu  +  3H20+2N,  thus  giving  a  new  quantity  of 
nitrogen. 

The  copper  thus  reduced  is  again  oxidized  by  the  oxygen  of 
the  air  setting  the  nitrogen  free;  these  two  reactions  really  take 
place  simultaneously.  The  gases  obtained  contained  greater  or 
lesser  quantities  of  ammonia  and  aqueous  vapor,  which  may  be 
easily  gotten  rid  of  by  suitable  means. 

The  chief  objection  to  these  processes  is  the  use  of  copper,  which 
is  an  expensive  metal,  even  in  Lupton's  process,  where  it  is  recovered, 
for  it  finally  undergoes  physical  modifications,  becoming  brittle 
and  falling  to  pieces,  which  prevents  its  being  suitable  for  further 
use. 

The  process  of  obtaining  nitrogen  by  the  combustion  of  char- 
coal in  a  current  of  air  has  the  objection  of  yielding  an  impure  gas, 
always  contaminated  with  carbonic  oxide,  and  even  with  a  small 
amount  of  oxygen. 

In  these  various  processes  the  oxygen  is  lost,  as  may  be  easily 
shown.  It  would  therefore  be  of  advantage  to  extract  these  two 
gases  simultaneously  from  the  atmosphere,  i.e.  to  utilize  the  residue 
from  the  preparation  of  oxygen,  a  residue  which  consists  entirely 
of  nitrogen. 

The  same  remark  may  be  made  concerning  the  utilization  of 
the  residual  gases  of  the  new  industry — the  manufacture  of  per- 
oxide of  sodium.  This  product  is  obtained  by  passing  a  current  of 
dry  and  pure  air  over  heated  sodium,  the  gaseous  residue  con- 
sisting chiefly  of  nitrogen. 

Any  of  the  methods  for  the  production  of  oxygen  from  air  may 
be  utilized,  among  which  may  be  mentioned  those  of  Boussingault, 
Tessie  du  Mothay  and  Marechal,  Mallet,  etc. 

Boussingault's  process  consists  in  fixing  the  oxygen  by  means 
of  baryta,  there  being  formed  barium  dioxide,  which  under  the  action 


120       METHODS   OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

of  A  heat  and  reduced  pressure  yields  one  molecule  of  oxygen,  with 
the  re-formation  of  baryta.  If  care  be  taken  to  add  certain  sub- 
stances so  as  to  prevent  fritting,  the  baryta  may  be  used  almost 
indefinitely.  This  process  has  the  advantage  of  being  rapid,  since 
•each  operation  for  the  complete  oxidation  and  deoxidation  lasts 
10  minutes,  and  140  may  be  made  per  day. 

The  process  of  Tessie  du  Mothay  and  Marechal  utilizes  a  mix- 
ture of  manganese  dioxide  and  caustic  soda.  When  this  mixture 
is  subjected  to  a  red  heat  in  a  current  of  air,  there  is  formed  sodium 
manganate, 

Mn02  +  2NaOH  +  0  =  MnO4Na2  +  H20, 

which,  when  heated  with  superheated  steam  at  450°,  liberates  oxy- 
gen and  yields  anew  the  original  substances, 

Mn04Na2  +  H20  =  Mn02  4-  2N20H  +  0. 

The  process  which  was  brought  out  in  1897  by  Etard  is  quite 
similar  to  the  above,  in  that  it  also  utilizes  the  oxygen  salts  of  man- 
ganese for  the  absorption  of  oxygen;  but,  as  Etard  himself  says, 
his  process  does  not  consist  of  a  simple  chemical  cycle:  it  is  based 
upon  a  state  of  equilibrium. 

If  potassium  permanganate  be  subjected  to  the  action  of  a  boil- 
ing alkali,  there  is  produced,  under  the  definite  conditions  of  pressure 
and  temperature,  a  liberation  of  oxygen, 

2Mn04K + 2KOH  =  2Mn04K2 + H20  +  0. 

The  reaction  is,  moreover,  a  reversible  one,  and  if  the  condi- 
tions of  temperature  and  pressure  are  changed,  the  manganate 
.absorbs  oxygen  of  the  air  and  yields  again  the  permanganate.  The 
nitrogen  set  free  may  be  collected  by  means  of  suitable  apparatus. 
On  account  of  the  separation  of  the  oxygen  and  the  nitrogen,  this 
process  should  be  tried  on  an  industrial  scale. 

As  early  as  1892,  Parkinson  installed  a  similar  process  in  Man- 
chester, which  produced  42  cubic  meters  of  oxygen  in  24  hours.  He 
uses  a  mixture  of  kaolin  and  permanganate,  which  is  heated  in 
retorts  at  a  reduced  pressure,  and  even  in  vacuum.  Under  these 
conditions  the  permanganate  yields  its  oxygen.  It  reabsorbs 
oxygen  when  heated  to  550°  C.  under  pressure  in  a  current  of  com- 
pressed and  hot  air.  There  are  five  retorts,  one  of  which  is  used 


MANUFACTURE  OF  CYANIDES.  121 

for  reheating  the  air.  This  air  is  compressed  by  means  of  a  pump 
in  a  compressor,  whence  it  is  driven  to  the  retorts  arranged  in  such 
a  manner  that  one  of  them  absorbs  the  oxygen  while  the  other  liber- 
ates it.  The  nitrogen  is  continually  removed  by  means  of  a  sniffling- 
valve,  and  the  separation  of  the  two  gases  is  automatically  regu- 
lated by  means  of  a  system  of  valves.  The  permanganate  mixture 
is  very  stable,  since  it  is  altered  neither  by  moist  air  nor  by  car- 
bonic acid. 

Numerous  patents  have  been  taken  out  in  regard  to  the  manu- 
facture of  oxygen,  but  they  are  only  more  or  less  successful 
modifications  of  the  processes  brought  out  by  Boussingault  and 
Tessie  du  Mothay. 

Mallet's  process,  which  is  likewise  much  to  be  recommended,  con- 
sists in  using  a  20%  solution  of  cuprous  chloride.  This  solution  is 
placed  in  a  retort,  which  is  heated  to  100°,  and  a  rapid  current  of 
air  is  passed  through.  The  cuprous  chloride  is  converted  into  the 
oxy  chloride,  which,  when  heated  in  the  same  retort  to  dull  redness, 
loses  its  oxygen  and  becomes  reconverted  into  the  cuprous  chloride. 

Several  years  ago  other  rather  ingenious  processes  were  shown. 
They  are  based  not  upon  chemical  reactions,  but  upon  purely 
physical  phenomena,  especially  those  of  dialysis  and  solubility. 

In  the  first  case  the  processes  are  based  upon  the  differences  exist- 
ing between  the  rate  of  dialysis  of  nitrogen  and  oxygen.  Of  such 
is  Villepigne's  process,  patented  in  1896.  This  consists  in  causing 
air  to  pass  through  a  series  of  membranes  made  of  caoutchouc, 
through  which  the  nitrogen  traverses  less  rapidly  than  does  the 
oxygen,  so  that  at  the  last  membrane  the  oxygen  emerges  almost 
pure,  leaving  the  nitrogen  behind  in  each  membranous  compartment, 
which  is  removed  by  special  means. 

It  is  not  known  that  such  processes  are  successful  or  that  they 
are  employed  on  an  industrial  scale.  Nevertheless  this  is  not 
the  last  to  be  heard  upon  this  subject,  and  the  future  will  probably 
show  us  what  to  expect  from  these  new  methods. 

Finally,  another  very  ingenious  process  must  be  mentioned, 
one  which  likewise  is  based  upon  the  difference  in  the  physical  prop- 
erties of  nitrogen  and  oxygen,  and  which  seems  to  merit  an  im- 
portant industrial  place.  This  is  the  process  of  Raoul  Pictet,  who 
is  already  well  known  in  the  scientific  world  through  his  remarkable 


122       METHODS   OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

researches  on  the  liquefaction  of  gases.  From  the  "  Bulletin  de 
la  Societe  des  Ingenieurs  civils, "  before  which,  on  June  7, 1901,  Pectet 
elaborated  his  new  process,  the  principal  features  are  here  extracted 
so  as  to  give  a  clear  idea  of  this  discovery. 

The  principle  of  this  method  is  as  follows:  The  point  of  lique- 
faction of  oxygen  under  atmospheric  pressure  is  about  - 183°,  whereas 
that  of  nitrogen  under  the  same  conditions  is  —195°.  Therefore 
the  nitrogen  is  sensibly  more  volatile  than  the  oxygen,  and  the 
difference  of  12°  which  exists  between  these  two  boiling-points 
differentiates,  as  the  theory  of  heat  shows,  at  such  low  tempera- 
tures, two  liquids  such  as  40°  would  differentiate  at  temperatures 
of  60°  to  100°. 

It  is  therefore  easy  to  see  that  if  a  mixture  of  these  two  gases., 
previously  liquefied,  be  vaporized,  it  will  be  possible  to  obtain, 
on  the  one  hand,  pure  nitrogen,  and,  on  the  other  hand,  equally  pure 
oxygen,  by  a  process  prefectly  analogous  to  that  upon  which  the 
system  of  fractional  distillation  depends.  Nevertheless  the  problem 
is  inverted,  from  a  practical  point  of  view,  since  it  is  necessary  first 
to  liquefy  the  two  gases  and  then  to  vaporize  them  in  order  to  collect 
them  in  the  gaseous  state. 

Thus,  the  inventor  succeeds  in  separating  the  two  gases  on  an 
industrial  scale.  The  air  is  first  suitably  dried,  then  it  is  compressed 
into  an  apparatus  completely  immersed  in  liquid  air.  Under  the 
influence  of  the  temperature  and  pressure,  this  air  is  in  its  turn  liquefied 
by  giving  up  its  latent  heat  of  condensation,  under  the  influence  of 
which  an  equal  quantity  of  the  liquid  air  of  the  container  becomes 
vaporized.  In  this  way,  with  a  very  slight  expense  of  energy  and 
a  definite  quantity  of  liquid  air,  unlimited  quantities  of  atmospheric 
nitrogen  and  oxygen  may  be  set  free.  Now,  the  difference  exist- 
ing between  the  points  of  liquefaction  of  these  two  gases  being 
known,  the  more  volatile  nitrogen  will  escape  before  the  oxygen, 
and  it  will  therefore  be  possible  to  collect  them  separately  by  means 
of  suitable  apparatus.  In  this  way  three  classes  of  gas  are  obtained: 

Nitrogen  purer  than 90.00% 

Oxygen  at  a  purity  of 50.55% 

Oxygen  purer  than 90.00% 

and  also  carbonic  acid,  which  always  exists  in  air,  and  which  is 
collected  in  the  solid  state. 


MANUFACTURE  OF  CYANIDES.  123 

As  will  be  seen,  this  is  a  most  ingenious  process,  practical  as  well 
as  ingenious,  and  likewise  not  at  all  expensive;  qualities  which  seem 
to  warrant  its  coming  application  on  an  industrial  scale. 

Having  firmly  established  the  theory  of  the  formation  of  cyanides, 
and  the  remarkable  role  which  is  played  by  atmospheric  nitrogen, 
it  was  immediately  attempted  to  turn  this  discovery  to  account. 
At  first  view,  and  at  least  theoretically,  nothing  seems  simpler  than 
to  combine  the  three  elements,  nitrogen,  carbon,  and  alkali  metal; 
but  the  experiments  undertaken  to  fix  the  nitrogen  of  he  ai:*  on  a 
practical  scale  have  not  always  given  results  which  would  lead  one 
to  expect  its  fulfillment.  Nitrogen  has  in  fact  quite  definite  nega- 
tive properties,  and  its  fixation  is  a  difficult  problem  which  has  not 
yet  been  solved  satisfactorily,  although  remarkable  progress  has 
been  made. 

The  first  attempts  to  fix  nitrogen  of  the  air  with  a  view  to  the 
production  of  cyanides  have  all  completely  failed.  Not  one  of  them 
obtained  the  support  of  the  manufacturer;  nevertheless  it  is  ex- 
tremely interesting  to  study  them,  for  they  are  a  step  toward  the 
truth,  and  they  have  had  an  incalculable  bearing  on  the  progress 
of  this  industry. 

Bunsen's  Process. — This  first  process  was  attempted  on  an 
industrial  scale  in  1845.  This  was  shortly  after  the  efflorescences 
of  potassium  cyanide  were  discovered  in  the  blast-furnaces.  Starting 
from  the  idea  that  the  potassium  cyanide  formed  was  due  to  the 
action  of  air,  Bunsen  constructed  a  special  blast-furnace  for  the 
production  of  potassium  cyanide.  Its  shape  was  similar  to  that  of 
ordinary  blast-furnaces.  It  was  filled  with  superposed  layers  of 
charcoal  and  potassa  and  heated  to  a  high  temperature  by  the 
combu  tion  of  a  portion  of  the  charcoal.  At  the  same  time  a  power- 
ful current  of  air  was  blown  through  the  mass  by  means  of  an  air- 
exhauster.  Under  these  conditions  cyanide  of  potassium  was  formed, 
which  flowed  through  the  lower  part  into  a  receiver  ad  hoc.  The 
product  thus  obtained  was  highly  contaminated  with  such  im- 
purities as  charcoal,  alkaline  salts,  and  mineral  salts,  due  to  the  ash 
of  the  combustible  material,  and  it  could  be  used  only  in  the  prepara- 
tion of  yellow  prussiate  of  potash.  Besides  this  serious  objection,  there 
were  others  no  less  serious,  such  as  the  losses  through  volatilization 
and  the  difficulty  of  conducting  such  an  operation,  especially  of  regu- 


124       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

lating  the  temperature  and  the  draft  of  air,  all  of  which  caused  the 
abandonment  of  this  process. 

Possoz  and  Boissiere  *s  Process. — This  process,  successively  put 
into  operation  at  Crenelle  and  at  Newcastle,  had  no  better  success. 
The  principle  is  the  same  as  in  Bunsen's  process,  differing  from  it 
only  in  the  modification  of  the  apparatus,  which  allowed  the  tem- 
perature and  the  intake  of  air  to  be  regulated.  Notwithstanding 
their  patient  efforts  and  an  unceasing  struggle  of  several  years, 
these  two  French  chemists  were  compelled  to  abandon  their  project, 
not  being  able  to  meet  foreign  competition,  which  sold  cyanide  at 
a  lower  price  than  theirs.  Yet  during  the  first  year  of  their  work 
at  Grenelle,  in  1843,  Possoz  and  Boissiere  succeeded  in  producing 
15  tons  of  an  excellent  quality  of  ferrocyanide.  But  the  high  cost 
of  fuel  and  of  refractory  brick  -at  Paris  compelled  them  to  go  to  Eng- 
land. After  completing  arrangements  with  Bramwell  and  Hughes, 
they  settled  at  Newcastle-on-Tyne,  where,  in  1844,  their  process 
was  established.  The  process  was  as  follows: 

Small  pieces  of  wood  charcoal  of  good  quality  were  saturated 
with  20  or  30%  of  caustic  potash,  or  of  carbonate  of  potash  moistened 
with  a  quantity  of  water  just  sufficient  to  dissolve  it.  After  desic- 
cation, this  material  was  charged  into  vertical  retorts  heated  on 
the  outside  in  a  furnace  at  white  heat. 

The  retorts  were  3.50  meters  long,  0.60  m.  outside  diameter 
and  0.492  m.  inside  diameter.  The  upper  portion  was  of  re- 
fractory clay  and  was  0.23  m.  in  thickness;  the  lower  part,  which 
served  as  cooling-chamber  for  the  cyanide  formed,  was  of  iron.  The 
height,  heated  to  white  heat,  was  246  millimeters.  A  portion  of  the 
gases  of  combustion,  quite  rich  in  nitrogen,  was  heated  to  a  white 
heat  by  passing  it  through  a  superheater,  where  it  was  compressed 
by  means  of  a  pump.  On  coming  out  of  the  superheater,  the  gases 
penetrated  into  the  retorts  through  small  lateral  slits.  After  10  hours' 
heating  and  action  of  the  gases,  the  cyanide  mixture  was  removed 
automatically  and  in  regulated  quantity  from  the  bottom  of  the 
retort.  This  mixture  was  allowed  to  fall  into  a  cooling-chamber 
and  thence  into  vats  containing  water  and  sulphate  of  iron.  By 
means  of  a  similar  automatic  system  a  new  charge  of  charcoal  and 
potassa  was  added  and  the  operation  repeated. 

Every  half   hour  the  apparatus  was   charged  with  an  amount 


MANUFACTURE  OF  CYANIDES.  125 

equal  to  15  kg.  wood  charcoal  containing  25%  potash,  and  a  corre- 
sponding quantity  of  cyanided  charcoal  was  removed.  The  opera- 
tion was  in  this  way  continuous. 

In  24  hours  each  apparatus  was  charged  with  720  kg.  dry  char- 
coal-potash containing  460  kg.  wood  charcoal  and  260  kg.  car- 
bonate of  potash.  During  the  operation  the  mass  decreased 
one  half  in  volume.  It  contained  from  30  to  50%  potassium  cya- 
nide. The  number  of  these  apparatus  was  twenty-four,  twenty  of 
which  were  in  operation,  two  ready  to  be  used,  and  two  being 
repaired.  Each  one  of  them  produced  50-70  kg.  of  ferrocyanide 
per  day. 

The  net  cost  at  the  works  in  Newcastle,  in  1846,  was  1.86  francs 
per  kilogram,  itemized  as  follows  on  the  basis  of  1000  kg.  of  ferro- 
cyanide of  potassium: 

7000  kg.  wood  charcoal,  crushed,  @2.50  fcs.  per  100  kg 175  fcs. 

1000  kg.  potash  from  America  @  50  fcs.  per  100  kg 500 

30  tons  coke  @  8  fcs 240 

20  tons  coal  @  2.50  fcs 50 

1  ton  carbonate  of  iron,  powdered 25 

120  men  and  children  (labor) 375 

Maintenance,  wear,  interest,  etc 500 

1865  fcs. 

Possoz  and  Boissiere's  process  was  in  operation  at  Newcastle 
during  the  three  years  1844  to  1847.  The  works  produced  1  ton 
of  potassium  ferrocyanide  regularly  per  day. 

That  is  certainly  an  appreciable  result,  but  when  the  process 
was  abandoned,  the  company  could  show  for  this  result  only  a  very 
large  deficit,  due  chiefly  to  the  rapid  wear  and  tear  of  the  apparatus, 
which  it  was  necessary  to  repair  frequently,  and  to  the  losses  in 
carbonates,  which  amounted  to  three  parts  for  every  one  part  of 
prussiate  produced.  Moreover,  the  amount  of  cyanided  charcoal 
to  be  subjected  to  lixiviation  was  far  too  small  in  proportion  to 
the  amount  of  ferrocyanide  obtained. 

Other  attempts  preceded  or  followed  that  of  Possoz  rnd  Bois- 
siere. But,  like  this  one,  they  also  proved  fruitless,  and  not  one  of 
them  has,  to  our  knowledge,  succeeded  in  giving  profitable  results. 


126      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

The  yield  was  too  small  to  produce  a  cyanide  capable  of  competing 
successfully.  To  understand  the  causes  which  made  these  processes 
abortive,  one  needs  only  to  consider  that  in  such  innovations  only 
4%  of  the  nitrogen  was  fixed,  that  the  high  temperatures  necessary 
in  these  processes  resulted  in  rapid  wear  and  tear  of  the  apparatus 
and  in  enormous  losses  through  volatilization,  and  that  moreover 
the  product  obtained  was  so  impure  that  it  was  necessary  to  purify  it 
.at  great  cost.  Yet  they  deserve  to  be  mentioned. 

Newton's  Process. — First   comes   Newton's   process   patented  in 

1843  in  England.     In  this  process  the  inventor  causes  the  gas  com- 
ing out  of  lead  chambers  to  pass  over  a  mixture  of  charcoal  and 
potash,  or  of  charcoal  impregnated  with  20-30%  carbonate  of  pot- 
ash heated  to  a  suitable  temperature.     The  yield  was  said  to  be 
50%  of  the  theoretical.     The  process  was  carried  on  from  1840- 
1847,  when  it  was  abandoned,  the  losses  in  carbonate  of  potash  being 
enormous  and  the  apparatus  deteriorating  rapidly.      Newton  noticed 
that  wood  charcoal  gave  better  results  than  coke,  that  potash  was 
preferable  to  soda,  that  the  yield  increased  with  increase  of  tem- 
perature, and  that  water-vapor  exerted  a  detrimental  action.     In 

1844  Sinndel  passed  nitrogen  over  charcoal  in  closed  vessels  at  a 
high  temperature. 

Blairs'  Process. — Blairs  caused  nitrogen  to  be  passed  over  a 
mixture  of  carbon  and  potassa  in  a  shaft-like  furnace,  which  was 
heated  by  a  grate  placed  in  the  exterior  casing.  The  products  of 
cyanide  and  potash  were  collected  in  chambers  or  in  ferric  solutions. 
The  residual  charcoal  was  treated  with  water  and  furnished  a  fresh 
amount  of  cyanide. 

Armengaud's  Process. — This  process  (1847)  differs  from  the  pre- 
ceding in  that  the  inventor  operated  in  the  presence  of  water.  All 
these  processes,  as  well  as  those  of  Alder  (1879)  and  Weldon  (1881), 
-differ  from  each  other  only  through  modifications  pertaining  to  the 
apparatus,  with  the  object  of  the  introduction  of  air  and  the  produc- 
tion of  heat. 

Margueritte    and    SourdevaPs    Process. — This   process    (1862)    is 

I   the  only  one  which  merits  more  attention.     The  inventors  sub- 

1  stituted    baryta    for    potassa    for    many    well-grounded    reasons. 

1  In    fact,    baryta    is    much    cheaper    than    potassa,    and    is    in- 

»  fusible   at   very   high   temperatures;    moreover,  as  is  well  known, 


MANUFACTURE  OF  CYANIDES.  127 

barium  fixes  nitrogen  with  great  ease.  (It  would  even  be  ideal  to 
find  masses  of  barium  or  calcium  in  order  to  fix  the  nitrogen  of  the 
air.  Lithium  has  also  been  mentioned,  but  it  is  a  rare  element 
and  too  difficult  to  prepare.)  It  attacks  the  apparatus  much  less 
than  does  potash,  and  the  wear  and  tear  of  the  vessels  is  diminished 
because  the  temperature  necessary  for  the  formation  of  barium 
cyanide  is  much  lower  than  that  of  potassium  cyanide. 

This  process  may  be  operated  in  different  ways.  First  a  mixture 
is  made  consisting  of  carbonate  of  barium  with  20  to  30  parts  of 
tar,  resin,  pitch,  wood  charcoal  or  coke,  which  mixture  is  heated 
to  high  temperature  under  the  action  of  a  current  of  air.  Under 
these  conditions  the  baryta  absorbs  nitrogen  with  ease,  with  forma- 
tion of  barium  cyanide,  which  is  converted  into  alkali  cyanide  by 
double  decomposition  by  the  reproduction  of  barium  carbonate  : 


2C+2N  +  Ba  =  (CN)2Ba, 
(CN)  2Ba  +  CO3K2  =  2NCK  +  C03Ba. 

This  is  one  of  the  rare  processes  invented  along  this  line  which 
has  given  good  results,  and  inventors  have  appeared  to  be  well 
satisfied  with  its  industrial  practicability. 

Mond's  Process.  —  Margueritte  and  Squrdeval's  process  was  taken 
up  in  America  in  1882  by  Mond,  who  modified  it  somewhat,  and 
who  obtained  from  it  good  results.  Mond  used  a  mixture  consist- 
ing of  charcoal,  magnesia,  and  carbonate  or  oxide  of  barium  pre- 
viously ignited  out  of  contact  with  air. 

According  to  his  German  patent  No.  21175  (1884),  he  operated 
as  follows: 

Briquettes  composed  of  a  mixture  of  witherite  (natural  carbonate 
of  barium),  pulverized  wood  charcoal  or  coke,  and  pitch  in  the  fol- 
lowing proportions: 

Carbonate  of  barium  ..............  32  parts 

Wood  charcoal  ....................     8    " 

Tar  ..............................  11     " 

These  briquettes  were  submitted  to  the  action  of  a  reducing 
flame  in  such  a  manner  as  to  char  the  pitch  and  to  dissociate  the 
carbonate  of  barium. 


128       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

They  were  then  ranged  in  an  annular  furnace,  where  there  was 
directed  a  current  of  gas  rich  in  nitrogen  and  as  poor  as  possible 
in  oxygen,  carbonic  acid  and  water-vapor;  for  example,  that  which 
escapes  from  the  carbonic-acid  absorption  apparatus  in  the  ammonia 
soda  process.  This  gas  was  previously  heated  to  a  temperature 
about  1400°.  In  order  to  do  that,  it  passed  through  into  the  first 
furnace  containing  briquettes  already  cyanated,  which  it  cooled 
while  at  the  same  time  heating  itself.  On  coming  out  of  this  fur- 
nace, it  passed  into  a  Siemens  regenerator,  and  from  there  into  the 
furnace  where  the  reaction  takes  place.  When  the  mass  was  thought 
to  be  sufficiently  cyanated,  it  was  drawn  out  of  the  furnace,  care 
having  first  been  taken  to  have  the  contents  of  the  furnace  cooled 
to  about  300°.  The  yield  was  about  40%. 

Weldon's  Process.^Weldon  (1879)  made  use  of  a  revolving 
furnace  similar  to  that  employed  in  the  manufacture  of  soda  and 
in  which  at  a  dull-red  heat  he  caused  nitrogen  to  act  upon  a  mix- 
ture of  charcoal  and  alkali. 

Fogarty's  Process. — To  the  above  must  be  added  the  processes 
patented  in  America  in  1883  and  1887  by  Fogarty  and  Dickson 
respectively. 

Fogarty  begins  by  producing  a  heating  gas  highly  superheated,, 
and  consisting  of  a  mixture  of  carbon  monoxide,  hydrogen,  and 
nitrogen.  Then  he  causes  this  gas  to  pass  into  retorts,  into  which 
he  transmitsi  n  the  same  direction  a  measured  volume  of  hydro- 
carbon vapors  obtained  from  the  distillation  of  oils.  The  mixture 
of  gases  comes  in  contact  with  a  definite  quantity  of  powdered 
incandescent  lime,  which  falls  from  the  top  of  the  retort.  This 
gas  contains,  therefore,  no  oxygen  nor  carbonic  acid  and  the  hydro- 
carbons are  consequently  broken  up  into  acetylene,  carbon,  and 
hydrogen,  which,  in  contact  with  lime  and  nitrogen,  produce  cal- 
cium cyanide. 

The  reaction  may  take  place  in  two  ways: 

(1)  Either  by  the  combination  of  nitrogen  and  calcium  with 
acetylene  at  the  temperature  at  which  this  gas  is  formed,  (2)  or 
by  the  union  of  nascent  carbon  produced  by  the  decomposition  of 
acetylene,  C2H2  =  C2  +  H2,  with  nitrogen  and  calcium. 

The  experiments,  of  Fogarty  justify  this  hypothesis,  the  most 
favorable  temperature  for  the  reaction  being  2200  to  2300°  F. 


MANUFACTURE  OF  CYANIDES.  129 

Dickson's  Processes. — Dickson  injected  a  mixture  of  air,  water- 
vapor,  and  powdered  charcoal  into  a  chamber  filled  with 
powdered  alkali  and  heated  to  a  proper  temperature,  naturally 
quite  high.  This  heat  was  produced  by  the  combustion  of  the 
gases. 

Lambilly's  Process. — Not  till  1889,  with  the  appearance  of  the 
processes  of  Lambilly  and  of  Chabrier,  have  real  improvements 
in  the  manufacture  of  cyanides  been  noted.  These  two  inventors 
sought  first  of  all  to  produce  ammonia  from  the  nitrogen  of  the 
air  by  passing  through  cyanides.  Their  various  patents  show  a 
•deep  knowledge  of  the  phenomena  of  cyanuration. 

The  first  two  of  these  patents  were  taken  out  with  a  view  espe- 
cially toward  the  production  of  ammonia  through  the  interme- 
diary of  the  cyanides.  The  first  one  (No.  199977),  taken  out 
August  8,  1889,  is  based  on  the  following  well-known  facts: 

(1)  The  volatile  hydrocarbons  are  decomposed  at  a  red  heat 
into  hydrogen  and  more  condensed  carbides. 

(2)  When  nitrogen  comes  in  contact  with  nascent  hydrogen,  it 
unites  with  it  to  form  ammonia  if   the  temperature  is  lower  than 
that  of  the  decomposition  of  this  latter  body. 

(3)  The  oxides  of  the  alkalis  or  alkaline  earths  are  reduced  in 
the  presence  of  charcoal  and  absorb  nitrogen  in  order  to  form  cya- 
nides at  temperatures  naturally  varying  with  the  kind  of  oxidizing 
agent  used. 

The  inventors  proposed  to  operate  this  process  on  an  industrial 
scale  as  follows: 

The  hydrocarbon  gas  is  produced  by  the  distillation  of  coal, 
wood,  peat,  petroleum;  the  nitrogen  is  obtained  from  the  atmosphere 
from  which  it  is  extracted  by  processes  already  known  (those  of 
Tessier  du  Motay,  Boussingault,  or  Mallet).  It  is  mixed  with  the 
carbide  gas  in  amounts  varying  with  the  composition  of  the  hydro- 
carbon. This  gaseous  mixture  passes  through  a  series  of  cylindrical 
retorts  arranged  in  one  or  more  furnaces.  These  retorts  are  charged 
with  a  mixture  of  charcoal  and  oxide  of  alkali  or  alkaline  earth 
and  the  whole  heated  to  redness.  The  inlet  of  gas  is  stopped  when 
the  amount  already  taken  in  is  judged  to  be  sufficient  to  convert 
the  contents  of  the  retorts  into  cyanide.  Under  these  conditions 
the  hydrocarbon  gas  is  broken  up.  Its  decomposition  goes  on 


130       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

and  is  completed  at  the  temperature  at  which  it  begins,  if  care  be 
taken  to  remove  the  gases  formed  from  the  atmosphere  in  contact 
with  the  substance  undergoing  dissociation,  in  such  a  manner  that 
the  pressure  is  always  less  than  the  tension  of  dissociation.  This 
condition  is  found  fulfilled;  in  fact,  the  formation  of  ammonia  by 
the  union  of  nascent  hydrogen  and  nitrogen  takes  place  with  con- 
traction. There  is  thus  produced  a  partial  vacuum  which,  together 
with  the  carrying  away  of  the  ammonia,  causes  a  pressure  inferior 
to  the  tension  of  dissociation.  The  carbon  of  the  carbide,  being 
in  the  nascent  state  in  the  presence  of  nitrogen  and  of  substances 
capable  of  becoming  converted  into  cyanides,  yields  this  latter 
body.  According  to  the  inventors,  if  the  conditions  of  temperature 
and  pressure  are  fulfilled,  it  is  possible  to  fix  an  amount  of  nitrogen 
corresponding  theoretically  to  the  hydrogen  and  to  the  carbon 
of  the  carbides  used. 

An  ingenious  modification  of  the  above  process  is  that  brought 
out  by  Lambilly  and  Chabrier  in  the  second  patent  (No.  202700) , 
of  December  21,  1889.  It  consists  in  removing  the  hydrogen  from 
the  mixture  of  hydrocarbons  and  nitrogen  before  its  entrance  into 
the  cylinder  where  the  conversion  into  cyanide  is  to  take  place, 
and  for  the  following  reasons: 

Illuminating-gas  is  composed  of  methane  and  ethylene,  which 
are  broken  up  at  red  heat  into  hydrogen  and  acetylene.  In  the 
presence  of  nitrogen  and  of  bodies  which  may  be  converted  into 
cyanides,  acetylene  gives  rise  to  these  latter,  but  the  hydrogen  set 
free  with  acetylene  through  the  decomposition  of  the  hydrocarbon 
places,  because  of  its  tendency  to  recombine  with  the  acetylene, 
a  serious  obstacle  in  the  way  of  the  formation  of  cyanogen,  which 
therefore  takes  place  but  slowly.  It  is  therefore  necessary  to  rapidly 
remove  this  hydrogen,  by  combining  it  with  nitrogen  under  the 
form  of  ammonia,  before  the  appearance  of  the  mixture  of  acety- 
lene and  nitrogen  into  the  cylinder  where  the  cyaniding  is  to  take 
place.  For  this  purpose  the  gas  first  passes  through  a  cylinder 
containing  oxide  of  copper,  obtained  from  the  process  of  extracting 
atmospheric  nitrogen  by  the  use  of  this  metal.  It  reduces  the  oxide 
of  copper  and  thus  forms  anew  the  metal,  which  may  be  used  in 
the  preparation  of  fresh  quantities  of  nitrogen.  The  hydrogen  being 
eliminated  by  this  means,  the  gaseous  mixture,  which  consists  now 


MANUFACTURE  OF  CYANIDES.  131 

of  only  acetylene  and  nitrogen,  passes  into  the  second  cylinder 
containing  the  substances  to  be  converted  into  cyanide.  The  flow- 
ing and  the  outlay  of  gas  and  of  nitrogen  are  regulated  through 
the  result  of  the  combinations.  The  inventors  claim  that  in  this 
way  a  minimum  of  1  cubic  meter  of  nitrogen  may  be  fixed;  that 
is,  1.25  kg.  per  cubic  meter  of  illuminating-gas  used. 

In  his  patent  No.  210365  of  December  20,  1890,  Lambilly  seeks 
only  the  production  of  cyanides.  This  patent  is  extremely  inter- 
esting, its  chief  object  being  to  produce  nascent  carbon,  which  renders 
its  union  with  nitrogen  all  the  easier. 

It  still  depends  on  the  decomposition  of  illuminating-gas  in  an 
atmosphere  of  nitrogen  and  in  the  presence  of  substances  capable 
of  being  converted  into  cyanides.  But  the  decomposition  of  the 
gas  is  carried  on  under  certain  conditions  which  permits  a  gas 
extremely  rich  in  acetylene  (C2H2)  to  be  obtained,  which  is  finally 
resolved  into  its  elements.  In  order  to  carry  on  this  dissociation, 
the  inventor  starts  from  the  consideration  that  illuminating-gas 
is  a  mixture  varying  more  or  less,  according  to  its  method  of 
preparation,  in  the  amounts  of  hydrogen  (a  gas  containing  the 
least  possible  amount  of  this  element  should  be  prepared),  and 
the  three  hydrocarbons,  ethylene,  methane,  and  acetylene,  and  that 
these  three  bodies  are  decomposable  at  different  temperatures. 
In  fact,  acetylene  is  broken  up  into  its  elements  only  in  the  neigh- 
borhood of  a  white  heat,  while  at  a  red  heat  ethylene  breaks  up 
into  acetylene  and  hydrogen,  or  methane  and  hydrogen,  or  a  mix- 
ture of  these  three  gases  according  to  the  degree  of  redness  and 
the  time  to  which  it  is  subjected  to  this  temperature.  Methan 
is  decomposed  at  a  like  low  temperature  into  acetylene  and  hydro- 
gen. From  these  facts  the  inventor  concluded  that  if  care  be 
taken  at  the  beginning  to  limit  the  action  of  the  temperature, 
only  the  ethylene  and  methane  will  be  decomposed,  forming  a 
mixture  very  rich  in  acetylene,  which  will  combine  with  the  acetylene 
already  existing  normally  in  the  gas.  Then  by  raising  the  tem- 
perature to  a  white  heat,  the  acetylene  will  in  its  turn  be  dissoci- 
ated into  its  elements. 

The   manufacture   of  cyanides   by   this  method  will  therefore 
comprise  four  phases: 

(1)  The  preparation  of  nitrogen. 


132       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

(2)  The  preparation  of  illuminating-gas. 

(3)  The    dehydrogenation,  or,    better,  the    carbureting   of   the 
Hatter. 

(4)  The  conversion  into  cyanides. 

The  nitrogen  is  prepared  as  in  the  previous  method,  by  passing 
air  over  copper  heated  to  dull  redness.  The  gas  is  prepared  by 
the  usual  methods,  then  freed  from  its  hydrogen  by  passing  it 
over  copper  oxid  produced  in  the  preparation  of  nitrogen.  The 
mixture  which  is  to  be  converted  into  cyanide  is  composed  of  char- 
coal and  oxids  or  carbonates  of  the  alkalis  or  of  barium  finely 
powdered.  This  is  placed  in  cylindrical  retorts  and  heated  to  a 
.high  temperature,  which  should  not,  however,  reach  a  white  heat. 

Right  here  Lambilly  improved  the  methods  of  his  predecessors  in 
two  important  particulars  viz.,  in  the  use  of  the  materials  for  manu- 
facturing cyanides.  Having  noticed  that  when  the  alkali  and  charcoal 
.are  heated  there  is  formed  a  considerable  amount  of  carbon  monoxid, 
which  prevents  the  intimate  contact  of  the  substances  which  are 
to  be  converted  into  cyanide  with  the  current  of  nitrogenized  and 
carbonized  gas,  he  avoids  the  passing  of  this  gas  just  as  soon  as 
the  temperature  is  favorable  for  the  formation  of  cyanides,  and 
removes  the  carbon  monoxid  as  fast  as  it  is  formed.  For  this  pur- 
pose he  makes  use  of  the  principle  established  by  Sainte-Claire 
Deville1,  that  the  dissociation  of  a  body  continues  and  ends  at  the 
temperature  at  which  it  begins  provided  care  be  taken  to  remove 
the  products  of  dissociation.  In  this  way  Lambilly  economizes 
fuel,  for  the  dissociation  of  the  alkali  oxid  takes  place  at  a  rela- 
tively moderate  temperature,  and,  moreover,  he  uses  the  carbon 
monoxid  in  heating  the  furnaces  in  which  the  cyaniding  process 
proceeds.  From  the  moment  carbon  monoxid  ceases  to  be  formed, 
he  allows  the  mixture  of  gas  and  nitrogen  to  pass. 

The  second  improvement  quite  naturally  follows  from  the 
first. 

In  fact,  being  no  longer  troubled  by  carbon  monoxid,  the  mix- 
ture of  gas  and  nitrogen  may  be  allowed  to  come  under  pressure 
into  the  cylinder  where  the  cyaniding  process  goes  on,  by  giving 
to  the  hydrogen,  which  is  the  residue  of  the  reaction,  but  a  limited 
outlet.  In  this  way  a  more  intimate  contact  of  the  substances 
to  be  converted  into  cyanides  with  the  reacting  gases  is  obtained, 


MANUFACTURE  OF  CYANIDES.  133 

In  order  to  hasten  the  decomposition  of  the  carbides  and  the 
foimation  of  the  cyanides,  Lambilly  proposes,  moreover,  to  add 
to  the  mixture  of  charcoal  and  alkali  a  certain  proportion  of  small 
pieces  of  nickel,  iron,  or  cobalt,  which  exert  a  decomposing  action 
on  the  carbides,  and  which,  becoming  heated  more  easily  than  does 
the  mixture  which  is  to  be  converted  into  cyanide,  yields  to  this 
mixture  a  part  of  its  heat. 

The  examination  of  these  methods  shows  that  the  inventor 
strove  always  to  produce  more  and  more,  in  a  state  as  near  as  pos- 
sible to  the  nascent  state,  substances  which  are  to  react  upon  one 
another.  This  is  the  object  of  the  later  patent  dated  December 
31,  1900,  and  which  allows  the  carbon  monoxid  produced  in  the 
reduction  of  the  alkali  oxids  to  be  profitably  utilized. 

Lambilly  proposes  to  collect  this  carbon  monoxid  in  a  gasometer, 
then  to  mix  it  with  a  quantity  of  illuminating-gas  such  that  the 
hydrogen  resulting  from  the  decomposition  of  the  latter  may  com- 
bine with  the  whole  of  the  oxygen  of  the  carbon  monoxid,  the  acety- 
lene thus  formed  yielding  a  fresh  amount  of  carbon  in  the  nascent 
state.  This  ingenious  arrangement  economizes  more  than  half 
the  illuminating-gas. 

In  his  German  patent  No.  6377  (November  14,  1890,  March  14, 
1892),  the  only  new  fact  given  by  Lambilly  is  the  manner  in  which 
he  obtains  the  alkaline  mixture  which  is  to  be  converted  into  cyanide. 
In  order  to  make  caustic  the  alkali  or  alkaline  earth  which  is  to 
be  used  in  producing  cyanide,  carbonate  of  potash  or  of  barium 
is  used,  and  in  order  to  render  them  porous  and  permeable  to  the 
action  of  the  reacting  gases,  there  is  added  for  each  equivalent  of 
carbonate  used  (69  kg.  K2C03  or  98  kg.  BaC03)  20  kg.  of  charcoal 
and  a  like  amount  of  quicklime.  The  whole  is  worked  up  into 
a  dry  powder,  introduced  into  horizontal  cylinders  connected  with  a 
vacuum  pump,  and  heated  under  as  perfect  a  vacuum  as  possible. 
Under  these  conditions  the  carbonate  becomes  caustic,  and  the 
carbonic  acid  produced  by  the  reaction  is  reduced  on  contact  with 
the  charcoal  into  carbon  monoxid,  which  is  utilized  as  fuel.  The 
inventor  also  states  the  amount  of  pressure  under  which  he  trans- 
mits the  mixture  of  illuminating-gas  and  nitrogen  into  the  cyaniding 
cylinders.  This  pressure  should  equal  10-15  centimeters  of  mer- 
cury. 


134       METHODS   OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

The  processes  of  Lambilly  are  still  far  from  being  perfect;  yet 
they  are  extremely  interesting  to  remember.  At  the  time  of  their 
appearance  they  produced  certain  practical  results  which  were 
by  no  means  to  be  despised.  Besides  they  show  a  considerable 
progress  over  the  first  synthetic  processes  used,  a  progress  obtained 
through  a  profound  study  of  the  complex  reactions  which  take 
place  in  the  formation  of  cyanides,  and  which  are  the  result  of  wise 
observations  and  of  the  patient  efforts  of  their  inventor.  One 
could  almost  affirm  that  they  paved  the  way  for  the  really  synthetic 
processes. 

The  following  processes  produce  cyanides  by  the  action  of  nitro- 
gen on  a  mixture  of  caustic  alkali  or  carbonate  of  alkali  and  char- 
coal. They  differ  but  little  from  one  another. 

Gilmour's  Process. — First  comes  this  process  (French  patent 
No.  233175,  October  2,  1893;  German  patent  No.  8475,  September  2y 
1893).  It  consists  in  producing  cyanide  compounds  by  the  action 
of  atmospheric  nitrogen  on  a  mixture  of  alkali  and  charcoal  heated 
to  1000°. 

The  various  caustic  alkalis  or  their  carbonates  may  be  used 
at  will;  however,  the  inventor  prefers  the  use  of  caustic  potash. 
These  substances  are  mixed  in  about  equal  proportions  with  char- 
coal, the  mixture  is  placed  in  suitable  recipients  through  which 
nitrogen  extracted  from  air  is  made  to  pass  until  the  mass  is  more 
or  less  transformed  into  cyanide.  The  vessels  are  then  emptied 
and  the  resulting  product  treated  with  water.  The  hydrocyanic 
acid  of  the  cyanides  in  solution  is  displaced  by  means  of  a  current 
of  carbonic  acid  (this  is  preferably  done  at  boiling  temperature 
and  under  atmospheric  pressure),  and  absorbed  in  a  concentrated 
solution  of  caustic  soda,  where  it  forms  sodium  cyanide,  which  is 
separated.  The  carbonic  acid  is  produced  by  the  combustion  of 
charcoal  in  air,  an  operation  which  allows  the  production  of  nitrogen 
necessary  for  the  first  reaction.  Moreover,  this  carbonic  acid  pro- 
duces anew  the  alkali  used  for  the  cyaniding  process. 

Young's  Process. — This  process  (English  patent  No.  24856,  Dec. 
27,  1893)  is  but  slightly  different.  The  cyanide  is  obtained  by  pass- 
ing a  mixture  of  air  and  hydrocarbon  vapors  over  the  following 
mixture  heated  at  a  high  temperature  in  iron  or  earthen  retorts  or 
in  suitable  furnaces: 


MANUFACTURE   OF  CYANIDES.  135 

Caustic  or  carbonate  of  alkali 4  parts 

Hydrate  or  carbonate  of  alkaline  earth 1  part 

Coke  or  coal 2  parts 

The  resulting  product  is  treated  with  water  in  order  to  extract 
the  cyanide.  When  the  temperature  is  too  high  a  portion  of  the 
cyanide  distils.  This  portion  may  be  collected  by  causing  the  gases 
with  which  it  is  carried  away  to  pass  through  a  layer  of  vegetable 
fibres. 

William  Donnell  Mackey's  Process. — This  process  (French  patent 
No.  243136,  Nov.  25,  1894;  German  patent  No.  87366,  Nov.  28,  1894) 
is  quite  similar  to  that  of  Bunsen.  It  consists  simply  in  subjecting 
to  a  powerful  current  of  air  a  mixture  of  coal,  wood  charcoal,  or 
coke,  lime,  potash,  or  any  other  alkaline  compound  which  may  be 
reduced  by  the  charcoal.  This  mixture  is  charged  in  a  specially 
constructed  furnace  A  (Fig.  3)  through  the  hopper  E  and  heated 
to  a  very  high  temperature.  The  furnace  is  vertical  and  quite 
large.  It  is  provided  with  lateral  openings  to  which  are  joined 
two  series  of  tuyeres.  These  are  arranged  in  two  series,  BB  and  CC, 
one  at  one  eighth  the  height  of  the  furnace,  the  other  at  about  the 
middle. 

The  cyanide  formed  is  sucked  away  by  a  machine  through  the 
opening  D  situated  in  the  space  included  between  the  two  series 
of  tuyeres. 

Thes  are  worked  by  a  powerful  bellows.  The  cyanide  is  col- 
lected and  condensed  according  to  ordinary  methods. 

The  gases  produced  through  combustion  escape  through  the 
horizontal  pipe  F. 

Readmann's  Process. — Readmann's  process  (French  patent  No. 
243129,  Nov.  26, 1894,  March  12, 1895)  differs  from  Gilmour's  process 
just  cited  only  in  the  fact  that  the  inventor  uses  the  electric  arc 
in  order  to  produce  the  necessary  temperature.  In  this  way  he 
claims  that  all  waste  and  destruction  of  apparatus  is  avoided  because 
he  develops  the  heat  in  the  very  mass  itself  by  means  of  carbon 
electrodes  or  electrodes  of  other  suitable  materials. 

The  mixture  to  be  con  verted  into  cyanides  is  composed  as  follows: 

Carbonate  of  barium  (perfectly  dry) 50  kg. 

Powdered  charcoal  (wood  charcoal  or  oil  or  coke).  . .  10  " 


136       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

The  carbonate  of  barium  may  be  replaced  by  any  other  car- 
bonate or  oxid  of  alkali  or  alkaline  earth. 

The  intimate  mixture  of  these  substances  is  introduced  into 
the  crucible  which  contains  coke  previously  heated  to  incandescence. 
As  source  of  nitrogen  the  inventor  uses  air  more  or  less  deoxygenized, 
or  water-gas,  whose  denitrified  residue  may  be  used  either  as  fuel 
or  for  illuminating  purposes.  The  cyanide  formed  flows  out  through 


FIG.  3. — Mackey's  Process. 

a  lateral  opening  situated  on  the  bottom  of  the  crucible.  The 
volatilized  portion  carried  off  with  the  remaining  gases  passes  into 
a  receiver  or  condenser,  where  it  is  absorbed  by  well-known 
methods. 

Mehner's  Process. — Ch.  Mehner  of  Charlottenburg  has  patented 
a  similar  process,  which  consists  in  passing  a  current  of  hot  air,  or 


MANUFACTURE  OF  CYANIDES.  137 

of  any  other  gas  rich  in  nitrogen,  over  a  mixture  of  coke  and  car- 
bonate of  alkali  or  alkaline  earth  heated  to  a  white  heat  in  the 
vat  of  an  electric  oven.  The  volatilized  cyanide  together  with 
the  other  gases  are  conducted  into  a  system  of  condensers  filled 
with  coke  placed  above  the  level  of  the  electrodes. 

Swan  and  Kendall's  Process. — In  order  likewise  to  avoid  the 
wear  and  tear  of  the  apparatus,  Swan  and  Kendall  have  devised 
an  ingenious  though  complicated  arrangement  the  net  cost  of  which 
must  be  quite  high  (French  patent  No.  252071,  Nov.  24,  1895,  and 
March  13, 1896,  and  German  patent  No.  87786,  Nov.  28,  1895).  It 
consists  of  an  inner  vessel  constructed  of  thin  sheets  of  nickel  or 
cobalt,  surrounded  by  another  larger  vessel  made  of  refractory 
earth.  This  apparatus  is  placed  in  an  oven  which  is  slightly  inclined. 
The  inner  vessel  is  provided  with  a  platinum  extension.  Hydrogen 
circulates  in  the  annular  space  between  the  nickel  vessel  and  its 
refractory  sheath;  its  object  is  to  prevent  the  metal  from  being 
attacked.  First  a  mixture  of  carbon  and  tungsten  is  prepared, 
consisting  of  100  parts  of  the  former  to  15  parts  of  the  latter,  by 
moistening  granular  or  powdered  charcoal  with  a  solution  of  potas- 
sium tungstate,  drying,  and  igniting.  This  mixture  is  placed  in 
the  inner  vessel;  a  current  of  nitrogen  extracted  from  air  is  passed 
through  and  the  temperature  raised  to  redness.  When  this  tem- 
perature has  been  attained,  melted  carbonate  of  potash  in  variable 
amounts  is  poured  into  the  crucible.  The  cyanide  formed  flows 
out  through  the  platinum  extension  as  fast  as  it  is  produced.  Tung- 
sten may  be  replaced  by  titanium,  molybdenum,  chromium,  or 
manganese. 

Pestchow's  Process. — In  his  process,  Pestchow  of  Dantzig  (Ger- 
man patent  No.  94114,  Dec.  8,  1896)  has  not  introduced  any  great 
modifications. 

It  consists  in  causing  a  current  of  nitrogen  containing  or  free 
from  oxygen,  mixed  with  or  free  from  ammonia,  and  carrying 
a  certain  amount  of  hydrocarbon — e.g.  acetylene — or  powdered 
charcoal,  to  act  on  an  alkali  bath  kept  in  a  state  of  fusion.  This 
bath  is  placed  in  a  covered  crucible  provided  with  an  opening  through 
which  the  nitrogen  gas  mixed  with  hydrocarbons  passes.  The 
nitrogen  should  always  be  in  excess,  but  not  the  carbon.  To  the 
alkali  bath  may  be  added  a  certain  amount  of  cyanide  from  a  pre- 


138       METHODS   OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

vious  operation  in  order  to  raise  the  temperature  of  the  fused 
mass. 

Chipmann's  Process. — The  latest  process  of  this  class  is  that  of 
Chipmann,  at  Johannesburg  (French  patent  Nos.  275570,  March  4, 
1898,  and  275488,  March  9, 1898),  which  produces  at  the  same  time 
cyanide  and  sulphocyanide  by  the  action  of  a  current  of  nitrogen 
to  which  sulphurous  acid  has  been  added,  on  a  mixture  of  charcoal 
and  oxid  or  carbonate  of  alkali  or  alkaline  earth. 

First  a  mixture  of  equal  parts  of  charcoal  and  oxid  or  carbo- 
nate is  made.  Preferably,  carbonate  of  barium  is  used. 

This  mixture  is  heated  to  about  1000°  in  suitable  vessels;  then 
a  current  of  sulphurous  acid  free  from  oxygen  is  passed  until  the 
whole  mass  has  been  converted  into  cyanide  and  sulphocyanide. 
IVhen  this  result  has  been  attained,  the  vessel  is  emptied  and  the 
product  treated  with  water.  Into  the  solution  thus  obtained,  heated 
to  boiling  and  after  the  addition  of  an  oxidizing  agent,  when 
necessary  a  current  of  air  is  made  to  bubble  under  atmospheric 
pressure. 

The  carbonic  acid  of  the  air  precipitates  the  barium  as  carbo- 
nate, which  is  collected,  dried,  and  used  over  again.  The  hydro- 
cyanic acid  set  free  passes  into  condensers  containing  a  concen- 
trated solution  of  caustic  soda  kept  at  a  temperature  of  40°  F.  The 
sulphurous  acid  produced  by  the  decomposition  of  the  sulphocyanide 
is  collected  with  the.  nitrogen  and  used  in  the  next  operation. 

Most  of  these  processes  have  had  but  a  short  life  industrially. 
That  is  because  the  circumstances  which  affect  the  yield  are  numer- 
ous, and  a  simple  thing  may  change  and  at  the  same  time  modify 
the  nature  of  the  reactions.  They  are  therefore  but  very  imper- 
fect methods,  to  which  many  and  serious  disadvantages  are  inherent. 

The  temperature  necessary  to  carry  on  the  reaction  is  in  all 
cases  very  high:  in  some  cases  a  white  heat,  in  other  cases  a  cherry- 
red  heat.  In  all  cases  the  heat  must  be  sufficient  to  cause  the  reduc- 
tion of  the  alkali  compound  used,  and  there  are  few  apparatus  which 
are  capable  of  resisting  such  a  high  temperature  without  wear  and 
deterioration.  Another  disadvantage  of  this  high  temperature 
is  in  the  loss  due  to  volatilization  either  of  alkali  or  of  cyanide, 
loses  which  sometimes  amount  to  considerable.  The  substances 
used  must  also  be  as  anhydrous  as  possible,  water  converting  the 


MANUFACTURE   OF  CYANIDES.  139 

cyanide  into  ammonia.  Nevertheless,  Langlois,  Kuhlmann,  Armen- 
gaud,  and  Ertel  have  shown  that  the  presence  of  a  very  small 
quantity  of  water  helps  along  the  reaction,  for  according  to  Kuhl- 
mann  the  production  of  cyanogen  is  preceded  by  the  formation  of 
ammonia. 

The  mixture  of  substances  to  be  converted  into  cyanide  must 
be  as  perfect  as  possible,  and  all  means  must  be  taken  to  make  it 
porous  and  permeable  to  the  action  of  the  reacting  gases.  The  yield 
decreases  in  proportion  as  the  cyanide  is  formed,  for  the  fragments 
of  the  mass  to  be  converted  into  cyanide,  and  especially  the  char- 
coal, becoming  imbedded  in  the  cyanide  and  melted  alkali,  come 
less  in  contact  with  the  gases.  If  the  contact  surface  of  these  sub- 
stances is  too  small,  the  same  trouble  is  met;  the  apparatus 
should  be  quite  large  in  order  to  present  as  much  surface  as  pos- 
sible to  the  action  of  the  nitrogenized  gas.  If  care  be  not  taken 
to  remove  the  products  as  fast  as  they  are  formed,  that  also  will 
impede  the  reaction,  which  will  either  be  stopped  or  rendered  slower. 

If  the  substances  under  treatment  contain  foreign  substances 
without  effect  on  the  reaction,  these  will  absorb  a  portion  of  the 
heat,  whence  comes  a  loss  of  calories.  Moreover,  these  bodies  pre- 
vent the  intimate  contact  of  the  products  of  the  reaction. 

Likewise,  if  the  gases  enclose  foreign  elements  such  as  oxygen, 
hydrogen,  carbon  monoxid,  or  carbonic  acid,  they  all  have  the 
disadvantage  of  diluting  the  nitrogen,  which  causes  the  reactions 
to  go  on  more  slowly.  Moreover,  each  one  of  them  exerts  a  detri- 
mental action  upon  the  reactions.  Thus  it  is  that  carbonic  acid 
oxidizes  the  charcoal,  and  possibly  also  the  cyanogen.  As  has 
often  been  demonstrated,  oxygen  and  cyanogen  cannot  coexist 
at  high  temperatures.  As  to  carbon  monoxid,  some  investigators 
attribute  to  it  an  injurious  action  in  that  it  prevents  intimate  con- 
tact of  the  cyaniding  masses  with  the  nitrogen,  whereas  others  look 
upon  it  as  favorable  to  the  reactions  because  of  its  reducing  prop- 
erties. 

The  formation  of  cyanides  in  these  various  processes  has  been 
the  subject  of  much  controversy. 

Relying  upon  many  experiments,  and  especially  upon  the  fact 
that  a  mixture  of  acetylene  and  nitrogen,  under  the  influence  of 
the  electric  spark,  yields  hydrocyanic  acid,  Berthelot  supposes 


HO       METHODS   OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

that  when  charcoal  and  potassa  are  strongly  heated  they  give  rise 
to  a  compound  C2K2,  which,  fixing  nitrogen,  then  yields  potassium 
cyanide,  CNK. 

Most  of  the  investigators  agree  in  saying  that  the  union  of  car- 
bon and  nitrogen  can  take  place  only  at  the  temperature  at  which 
the  alkali  metal  is  set  free.  This  hypothesis  is  confirmed  by  the 
very  fact  that  cyanogen  and  oxygen  cannot  coexist  in  the  same 
medium  at  a  high  temperature. 

As  to  the  alkali  metal,  some  investigators  attribute  to  it  a  simple 
contact  action,  and  its  object  would  therefore  be  to  fix  the  cyanogen 
just  as  fast  as  it  is  formed,  in  accordance  with  the  law  of  Sainte- 
Claire  Deville,  according  to  which  reactions  are  continued  and 
finished  quickly  if  care  be  taken  always  to  remove  the  products 
formed  as  fast  as  they  appear. 

Finally,  other  investigators  assert  that  there  is  first  a  formation 
of  an  alkali  nitride,  which  later  becomes  converted  into  cyanide 
through  the  action  of  carbon.  This  last  hypothesis  is  just  as  prob- 
able as  the  preceding  ones,  since  Center  and  Brieylieb  obtained 
cyanide  by  heating  magnesium  nitride  in  a  current  of  carbonic  acid 
or  carbon  monoxid. 

Several  processes  have  even  been  proposed  along  this  line,  e.g. 
those  of  Moise  (French  patent  246587,  April  22,  1895)  and  of  Mehner 
(French  patent  254273,  Feb.  26,  1896). 

Processes  of  Moise  and  Mehner.  —  Moi'se's  process  consists  in 
heating,  in  a  rotatory  oven  to  a  dull  red,  a  mixture  of  boron 
nitride,  alkali  carbonate,  and  charcoal  in  the  following  proportions: 

Boron  nitride  .............................     50  kg. 

Carbonate  of  alkali  (potassium)  .............  250  '  ' 

Charcoal  ..................................     30  " 

The  reaction  is  as  follows: 


Boron  nitride  is  obtained  by  heating  to  a  bright  red  for  one 
hour  the  following  finely  powdered  mixture: 

Sodium  borate  .............................  100  kg. 

Sal  ammoniac..,  ,  150  " 


MANUFACTURE  OF  CYANIDES.  141 

This  product  is  treated  with  boiling  water,  then  hydrochloric 
acid  is  added  in  excess,  yielding  a  precipitate  of  boron  nitride. 

Mehner  prepares  nitrides  of  boron,  silicium,  magnesium,  titanium, 
and  vanadium  by  reducing  the  oxids  of  these  metals  by  means  of 
carbon  in  the  midst  of  an  atmosphere  of  nitrogen. 

There  is  very  little  probability  that  these  processes  have  given 
any  practical  results,  and  we  doubt  very  much  whether  they  have 
ever  been  operated  industrially. 

Besides,  the  metals  which  these  investigators  used  in  the  prepa- 
ration of  the  nitrides  are  too  expensive  to  allow  these  processes 
to  be  used  practically  on  an  industrial  scale. 

All  these  processes  just  described  have  the  disadvantage  that 
they  do  not  produce  the  cyanide  directly;  hi  fact,  masses  contami- 
nated with  impurities  are  obtained  which  must  be  treated  with 
water  and  purified,  by  which  the  net  cost  is  increased.  It  has 
already  been  seen  that  other  equally  serious  disadvantages  are 
inherent  to  these  processes. 

It  has  already  been  stated  that  the  cyanide  is  formed  only  in 
case  the  alkali  metal  is  set  free.  It  was  therefore  quite  natural 
that  attempts  should  be  made  to  use  this  metal  in  the  free  state 
in  order  to  avoid  the  reduction  of  its  compounds  originally  used 
and*  consequently  the  many  disadvantages  resulting  therefrom. 
These  processes  may  really  be  designated  as  synthetic,  since  they 
start  with  three  bodies  in  the  free  state:  carbon,  nitrogen,  potas- 
sium or  sodium.  The  low  cost  of  the  alkali  metals  and  the  ease 
with  which  they  are  at  pres  nt  manufactured  permit  their  use  on 
an  industrial  scale.  Moreover,  the  cyanide  industry  creates,  by 
means  of  these  processes,  a  new  market  for  the  sodium;  its  use 
became  limited  when  it  was  no  longer  employed  in  the  manufacture 
of  aluminum.  The  experiments  carried  on  along  this  line  have 
been  satisfactory.  They  are  exceedingly  interesting  and  they  will 
therefore  be  described. 

Castner's  Process. — This,  the  first  one  of  these  processes,  was 
patented  by  Hamilton  Young  Castner  (No.  239643,  June  28,  1894). 
It  consists  in  the  action  of  a  current  of  nitrogen  on  charcoal  heated 
to  redness,  upon  which  melted  sodium  or  potassium  flows,  the  reac- 
tion being  as  follows: 

K  or  Na+C+N  =  CNK  or  CNNa. 


142       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

The  reaction  is  carried  on  in  a  vertical  iron  retort  (A,  Fig.  4) 
placed  in  a  furnace  and  capable  of  being  heated  to  redness.  This 
retort  is  provided  with  an  inlet  tube  B,  an  S-shaped  opening  at 
the  bottom  (7,  and  with  a  hopper  D. 


FIG.  4. — Castner's  Apparatus. 

The  retort  is  charged  with  wood  charcoal  through  the  hopper  D, 
which  is  afterward  closed.  The  opening  at  the  bottom  C  is  sealed 
at  the  elbow  E  by  means  of  cyanide.  The  temperature  is  raised 
to  redness,  then  a  current  of  nitrogen,  through  the  tube  F,  and 
melted  sodium  or  potassium,  through  the  inlet  tube  B,  are  let  in 
simultaneously.  The  alkali  metal  flows  gradually  through  the 
wood  charcoal  and  meets  the  nitrogen,  which  flows  in  the  opposite 
direction.  The  three  elements  combine  directly  and  form  cyanide, 
which  flows  through  the  opening  C  into  the  receiver  G.  The  unab- 
sorbed  gas  escapes  through  the  tube  77,  whence  it  may  with  advantage 
be  conducted  into  a  second  retort.  Charcoal  may  be  replaced  by 


MANUFACTURE  OF  CYANIDES.  143 

inert  substances  such  as  pieces  of  iron  or  of  porcelain,  in  which  case 
a  mixture  of  nitrogen  and  hydrocarbon  is  conducted  through  the 
mass.  The  alkali  metals  may  also  be  replaced  by  their  alloys;  e.g. 
lead  sodium. 

Castner  has  improved  this  process,  which  consists  in  using 
ammonia,  and  conducting  the  operation  in  two  stages.  This  modi- 
fied process  will  be  taken  up  at  length  when  discussing  the  ammonia 
processes.  Castner's  process,  properly  speaking,  belongs  to  that 
class  of  methods  using  atmospheric  nitrogen,  the  only  one  to  which  the 
term  synthetic  really  belongs,  but  to  our  knowledge  it  has  never 
given  results  permitting  its  use  industrially. 

Hornig  and  Schneider's  Process. — This  process  belongs  •  to  the 
same  class  as  that  of  Castner.  Castner's  process  consists  in  allow- 
ing nitrogen  to  act  upon  the  vapors  of  the  alkali  metals  in  the  pres- 
ence of  incandescent  charcoal;  Hornig  and  Schneider's  process 
uses'  the  alloys  of  the  alkali  metals  and  of  the  heavy  metals.  Both 
of  these  processes  using  nitrogen  or  ammonia  indifferently,  but 
preferably  the  latter,  will  be  studied  in  detail  in  the  chapter  devoted 
to  the  ammonia  processes. 

Mehner's  Process. — Mehner's  process  (1894-1895)  belongs  in 
some  respects  to  that  class  of  processes  using  atmospheric  nitrogen 

It  consists  in  electrolyzing  barium  cyanide  in  a  state  of  igneous 
fusion,  using  a  charcoal  cathode  and  in  the  presence  of  nitrogen  gas 
(Fig.  5). 

The  current  decomposes  the  barium  cyanide  into  hydrocyanic 
acid,  which  escapes  at  the  anode,  and  barium,  which  is  set  free  at 
the  cathode  at  a  rather  high  temperature,  close  to  its  boiling-point. 
Meeting  the  nitrogen,  which  is  in  contact  with  red-hot  charcoal 
at  the  cathode,  this  metal  reproduces  cyanide  of  barium,  which 
flows  in  the  bath  and  is  thus  subjected  to  electrolysis.  In  this  way 
the  process  may  be  continued.  With  the  same  quantity  of  cyanide 
somewhat  limited,  it  suffices  to  supply  carbon  and  nitrogen  and 
to  maintain  the  temperature  desired.  The  hydrocyanic  acid  gas 
formed  may  be  conducted  outside  and  absorbed  by  well-known 
means,  or  may  be  fixed  in  the  electrolyzer  itself  by  the  addition 
of  sea  salt,  which  under  the  action  of  the  current  breaks  up  into 
chlorine  and  sodium.  The  hydrocyanic  acid  set  free  at  the  posi- 
tive pole  in  a  separate  cell  may,  by  means  of  a  suitable  contrivance, 


144       METHODS    OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

react  upon  the  alkali  metal  displaced  and  yield  cyanide  of  sodium 
directly. 

The  last  class  of  processes  utilizing  atmospheric  nitrogen  is 
based  on  the  use  of  metallic  carbides.  It  has  already  been  stated 
that  many  investigators,  especially  Berthelot,  explained  the  for- 
mation of  cyanides  through  the  intermediary  of  carbides.  In 
Comptes  Rendus,  1894,  503,  Moissan  reported  that  when  nitrogen 
is  passed  over  heated  carbides  of  calcium,  barium,  or  strontium 
no  reaction  or  union  takes  place.  Frank  and  Caro  showed  that 


CAzH 


FIG.  5. — Mehner's  Apparatus. 

the  opposite  was  true  if  the  nitrogen  used  was  charged  with  a  cer- 
tain amount  of  aqueous  vapor.  In  this  case  cyanides  are  formed 
as  follows: 

C2M+2N=(CN)2M. 

Based  upon  this  reaction,  these  investigators  have  brought 
out  a  process  for  the  manufacture  of  cyanides  which  is  thought 
to  give  satisfactory  results.  Many  other  manufacturers  have  fol- 
lowed the  example  set  by  Frank  and  Caro,  and  have  had  similar 
processes  patented. 

Frank  and  Caro's  Process. — The  first  patent  taken  out  by  Frank 
and  Caro  dates  from  1895  (French  patent  No.  249539,  Aug.  10,  1895). 


MANUFACTURE  OF  CYANIDES.  145 

It  consists  practically  as  follows:  It  may  be  applied  equally  well 
to  the  carbides  of  the  alkaline  earths  or  alkalis,  either  pure  or  con- 
taining alkaline  earths  or  alkalis,  or  even  salts  of  these  bases.  A 
mixture  of  the  carbides  prepared  in  the  usual  manner  may  like- 
wise be  used;  but  according  to  the  opinion  of  the  investigators, 
barium  carbide  is  the  most  suitable. 

The  carbide  prepared  in  the  usual  way  is  disintegrated  and 
introduced  into  a  tubular  retort  of  refractory  material,  preferably 
clay.  This  retort  is  provided  with  suitable  tubes  for  the  inlet  and 
outlet  of  gases. 

The  necessary  nitrogen  is  taken  from  the  atmosphere.  Air 
either  wholly  or  partly  free  from  oxygen  may  be  used.  The  air 
is  charged  with  moisture  by  passing  it  through  a  vessel  containing 
water. 

The  retort  is  first  heated  almost  to  redness,  then  the  current 
of  nitrogen,  charged  with  moisture,  is  admitted  under  a  moderate 
pressure  and  at  such  a  rate  that  the  reaction  is  complete  in  about 
two  hours.  A  change  of  15  to  17  kg.  barium  carbide  requires  2  to 
2.5  cu.  m.  of  nitrogen. 

The  product  obtained  is  cooled,  then  taken  up  with  water.  The 
unconverted  carbide  yields  acetylene,  which  is  collected  separately. 
The  solution  contains  barium  cyanide  which  by  double  decom- 
position may  be  transformed  into  alkali  cyanide. 

Carbide  of  calcium  alone,  thus  treated,  does  not  yield  good 
results.  An  excellent  yield  is  obtained,  however,  by  using  a  mix- 
ture of  calcium  and  barium  carbides  or  of  carbides  of  calcium  and 
sodium  obtained  by  the  ordinary  methods  by  means  of  soda  lime 
and  charcoal.  The  product  of  the  reaction  is  treated  as  just  stated — 
i.e.  treated  with  water — the  acetylene  being  collected  separately 
and  the  solution  thus  obtained  converted  into  alkali  cyanide.  This 
latter  operation  may  be  brought  about  either  by  addition  of  an 
acid  or  preferably  by  conducting  carbonic  acid  through  the  solution, 
which  displaces  the  hydrocyanic  acid  gas,  which  latter  is  brought 
in  contact  with  the  metallic  oxid  of  the  cyanide  desired.  This 
may  likewise  be  effected  by  double  decomposition  by  the  addition 
to  the  solution  of  an  alkali  ca  bonate,  which  transforms  the  cyanide 
of  the  alkaline  earth  into  alkali  cyanide,  while  at  the  same  time 
the  carbonate  of  the  alkaline  earth  separates  out. 


146       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

The  result  given  by  the  treatment  of  the  carbides  of  barium 
or  calcium  may  be  improved  by  adding  to  the  carbides  or  to  their 
mixture  an  alkali  carbonate  or  hydrate. 

When  the  alkali  carbides,  whether  alone  or  mixed  or  even  in 
the  presence  of  an  alkaline  earth  or  its  salts,  are  subjected  to  the 
same  treatment  as  that  indicated  above  in  the  case  of  the  barium 
carbide,  they  yield  the  corresponding  cyanides,  which  may  easily 
be  extracted  with  water  from  the  product  of  the  reaction. 

The  most  favorable  temperature  for  these  reactions  is,  according 
to  the  investigators,  dull  redness.  If  a  lower  temperature  be  used 
the  action  of  the  nitrogen  takes  place  but  slowly,  while  if  the  tem- 
perature be  too  high  the  yield  decreases,  due  to  a  partial  decom- 
position. 

In  order  to  make  the  most  profitable  use  possible  of  the  nitrogen, 
several  retorts  may  be  used  in  a  series,  which  allows  a  continuous 
operation . 

In  the  certificate  of  improvement  joined  to  the  patent  just 
described,  Frank  and  Caro  replace  nitrogen  with  ammonia. 

The  investigators  state  that  in  practice  the  formation  of  cyanides 
depends  not  only  on  the  action  of  free  jdtrogen,  in  the  presence  of 
water- vapor,  on  the  carbides,  but  also  on  the  action  of  dry  nitrogen 
upon  impure  carbides  containing  oxids,  carbonates,  and  sulphates. 

Moreover,  the  chemically  combined  nitrogen  (ammonia  or 
the  oxids  of  nitrogen)  may  likewise  be  used  in  the  formation  of 
cyanides  by  means  of  carbides  if  the  nitrogen  compounds  used 
furnish,  during  their  action  on  the  carbides,  the  necessary  nitrogen, 
a  result  which  is  brought  about  through  dissociation  or  reduction 
by  means  of  carbides.  From  these  remarks  the  investigators  think 
that  the  oxids,  carbonates,  sulphates,  or  other  salts  induce  the 
reaction  in  the  same  manner  as  does  water-vapor,  the  use  of  which 
may  thus  be  suppressed.  This  action  of  foreign  salts  is  shown 
even  when  the  carbides  contain  only  very  small  quantities  of  them. 

Likewise,  with  the  object  in  view  of  avoiding  the  use  of  water- 
vapor,  the  inventors  of  this  process  recommend  the  use  of  ammonia, 
which  renders  the  action  of  moisture  superfluous. 

If  ammonia  be  passed  over  a  carbide  or  a  mixture  of  carbides, 
or  a  mixture  of  carbides  and  alkali  salts,  cyanide  is  formed.  During 
this  formation,  the  ammonia  becomes  dissociated  into  its  constitu- 


MANUFACTURE  OF  CYANIDES.  147 

ent  elements,  nitrogen  and  hydrogen.  The  nitrogen  becomes  fixed 
to  the  metal,  whereas  the  hydrogen  escapes,  and  may  be  collected 
separately  and  used  as  such  in  the  heating  of  the  apparatus.  The 
reaction  may  be  thus  interpreted: 

CaC2  +2NH3  =  Ca(CN)2+3H2. 


Although  the  presence  of  moisture  is  useless  in  starting  and 
completing  this  reaction,  it  does  not  modify  it  in  any  way,  and 
exerts  no  perceptible  action  on  the  yield.  Thus  ammonia-gas, 
whether  dry  or  moist,  could  be  used  equally  with  advantage. 

Continuing  their  researches  on  the  manufacture  of  cyanides 
by  means  of  carbides,  Frank  and  Caro  observed: 

(1)  That  the  formation  of  cyanides  by  the  processes  above 
mentioned  is  however  limited,  and  if  the  heating  be  carried  on  at 
least  up  to  a  dull  redness  and  does  not  exceed  a  bright  yellow,  a 
large  part  of  the  nitrogen  absorbed  by  the  carbides  is  combined 
at  the  expense  of  the  formation  of  other  nitrogenous  compounds. 
This  phenomenon  is,  according  to  them,  due  in  part  to  the  action 
of  cyanides  already  formed,  and  in  part  to  the  direct  action  of  the 
reacting  mass  according  to  the  two  general  equations 


z(2MCN)  +zN  =  z(M2NCN)  +  (CN)s, 
M2C2+N2=M2NCN+C. 

In  fact  Frank  and  Caro  discovered  that  the  reaction  masses 
contained  appreciable  amounts  of  metallic  derivatives  of  cyanamid, 
(M2NCN),  of  paracyanogen  (CN)z,  and  of  other  nitrogenous  com- 
pounds. 

(2)  That  the  formation  of  cyanamid  in  the  action  of  nitrogen 
on  carbides  must  be  due  to  an  excess  of  nitrogen,  which  condition 
may  take  place  from  the  time  that  this  gas  comes  in  contact  with 
the  carbide. 

(3)  That  the  formation  of  cyanamid  may  be  increased,  by  giving 
the  carbide  a  greater  surface,  either  by  powdering  it  or  by  making 
it  very  porous  and  allowing  the  nitrogen  to  act,  at  a  high  tempera- 
ture, varying  from  a  dull  red  to  incandescence,  upon  a  thin  layer 
of  carbide.     In  this  case  it  will  be  easily  understood  that  the  con- 
ditions will  be  eminently  favorable  for  the  formation  of  cyanamid, 


148      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

a  large  quantity  of  nitrogen  coming  in  contact  with  a  small  quantity 
of  carbide.  It  is  upon  this  series  of  remarkable  observations  that 
Frank  and  Caro  have  based  their  new  patent,  No.  289828,  Oct.  2, 
1899. 

Carbide,  or  a  mixture  of  two  or  more  carbides,  or  of  a  carbide 
with  other  salts  of  alkalis  or  alkaline  earth,  is  subjected  to  the 
action  of  nitrogen  or  of  ammonia  under  the  conditions  stated  above, 
with  the  view  of  favoring  the  production  of  cyanamid  and  of  its 
derivatives. 

The  substance  thus  obtained  is  then  converted  into  cyanide  by 
fusing  it  with  alkali  hydrate  or  carbonate,  which  may  be  added 
to  the  materials  of  the  reaction  before  or  during  fusion. 

If  the  mass  does  not  contain  sufficient  carbon,  set  free  by  the 
preceding  reactions,  it  is  well  to  add  suitable  quantities  thereof. 

Likewise,  if  the  materials  to  be  treated  contain  compounds  of 
nitrogen  which  are  not  combined  to  a  metal,  e.g.  paracyanogen, 
it  is  necessary  to  add  a  sufficient  quantity  of  a  base  in  order  to  com- 
bine the  cyanogen  formed. 

This  fusion  results  in  converting  the  metallic  compounds  of 
cyanamid  and  of  paracyanogen  into  cyanides  corresponding  to  the 
bases  used,  according  to  the  equations: 

(1)  M2NCN+C  =  2MCN    and 

(2) 


Generally  the  following  are  used: 

Oxid  or  carbonate  ..........................  1  part 

Salt  of  cyanamid  ..........................  2  parts 

It  is  best  to  treat  the  product  of  the  reaction  with  water,  then 
to  displace  the  hydrocyanic  acid  by  an  acid,  e.g.  carbonic  acid. 

The  cyanamid  remaining  in  solution  is  separated  by  shaking 
with  ether  or  other  solvent,  or  by  other  appropriate  means. 

While  studying  the  ammonia  processes  a  process  will  be  noted 
which,  although  it  does  not  utilize  the  carbides,  has  for  its  object 
the  production  of  cyanamid.  The  solution  of  the  problem  seems 
to  be  along  this  line.  Frank  and  Caro's  processes  certainly  de- 
serve to  be  kept  in  mind;  they  solve  the  problem  quite  satis- 
factorily and  in  an  economic  manner,  seeing  that  the  carbides  are 


MANUFACTURE  OF  CYANIDES.  149 

prepared  with  ease.  We  do  not  know  whether  these  methods 
have  been  adopted  on  an  industrial  scale,  though  they  were  to 
have  been  tried  in  some  Frankfort  works.  It  was  hoped  that  the 
experiments  undertaken  along  this  line  would  be  crowned  with 
success,  since  the  use  of  carbides  in  the  manufacture  of  cyanides 
would  open,  in  fact,  an  important  market  for  the  former. 

Unfortunately,  it  would  seem  that  the  works  at  Frankfort  have 
stopped  operation,  the  results  obtained  not  having  been  thought 
sufficiently  profitable  for  their  continuance. 

Other  methods  likewise  based  on  the  use  of  carbides  have  fol- 
lowed those  of  Frank  and  Caro. 

Process  of  the  "  Chemische  Fabrik  Pferse*e  Augsbourg." — In  the 
first  place  comes  this  process  (French  patent  No.  252943,  Jan.  3,  1896; 
English  patent  1022,  Jan.  15,  1896).  It  consists  in  allowing  free 
nitrogen  at  a  red  heat  to  act  upon  a  mixture  of  calcium  carbide 
(or  barium  carbide)  and  dry  alkali  carbonate. 

According  to  the  investigators  there  would  first  be  established 
a  reciprocal  reaction  between  the  alkaline-earth  carbide  and  the 
alkali  carbonate,  which  in  the  case  of  calcium  carbide  and  potassium 
carbonate  may  be  thus  expressed: 

CaC2+K2C03  =  C2K2+CaO+C02; 

the  carbonic  acid  would  be  immediately  reduced  to  the  state  of 
carbon  monoxid  by  means  of  a  small  amount  of  calcium  carbide 
in  excess. 

The  potassium  carbide  formed  would  then  absorb  the  nitrogen 
according  to  the  equation 

C2K2+2N=2CNK. 

The  reaction  takes  place  still  better  in  the  presence  of  ammonia : 
C2K2+2NH3=2CNK+6H. 

The  inventors  propose  to  apply  this  property  of  the  carbides 
to  the  old  process  of  manufacture,  which  consists  in  using  alkali 
carbonates,  organic  animal  substances,  or  nitrogenized  charcoal, 
and  to  ignite  the  whole  at  a  high  temperature.  By  adding  a  car- 
bide to  these  substances  the  reaction  would  take  place  at  a  lower 


150       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

temperature  than  that  thought  necessary  up  to  the  present  time 
and  the  yield  which  was  relatively  small  would  be  increased. 

The  advantages  which  would  follow  from  the  process  of  the 
Chemische  Fabrik  Pfersee  Augsbourg  would  be  the  following: 

(1)  An  appreciable  decrease  in  the  cost  of  fuel,  and  wear  and 
tear  of  the  apparatus  due  to  the  relatively  lower  temperature  of 
the  reaction. 

(2)  The  easy  and  abundant  absorption  of  nitrogen. 

(3)  The  obtaining,  under  the  form  of  cyanides,  of  the  almost 
theoretical  quantity  of  ammoniacal  nitrogen  used. 

These  last  two  points  should  be  verified  industrially. 

Beringer's,  Wolfram's,  and  Blackmore's  Processes. — Among  the 
other  methods  using  carbides  must  be  mentioned  that  of  Beringer 
(German  patent  20334,  Feb.-Nov.,  1897),  which  consists  in  passing 
nitrogen  over  carbides,  noting  that  the  conversion  into  cyanides  is 
complete  at  900°,  if  dry  and  pure  nitrogen  be  used,  a  condition 
which  would  complicate  the  solution  of  this  problem  from  an  indus- 
trial standpoint  (the  inventor  claims  that  the  reaction  begins  even 
at  about  450°  C.). 

Wolfram's  method  (1898)  consists  in  causing  a  metallic  carbide 
(alkaline?)  and  a  nitrogenous  compound  or  free  nitrogen,  preferably 
ammonia,  to  act  upon  an  alkali  hydrate  in  state  of  fusion. 

Blackmore's  method  (U.  S.  patent  No.  605694,  June,  1898)  seems  to 
complicate  instead  of  simplifying  matters.  The  inventor  proposes 
to  compress  the  nitrogen  into  a  mixture  of  alkali  sulphide  and  metallic 
carbide,  preferably  carbide  of  iron.  The  sulphide  becomes  converted 
into  the  corresponding  cyanide,  more  or  less  contaminated  with  ferro- 
cyanide  and  sulphocyanide,  according  to  the  amounts  of  the  charge 
and  the  conditions  of  the  reaction,  conditions  which  are,  moreover, 
not  stated  in  the  patent.  Besides,  the  complete  purification  of 
this  product  must  be  rather  expensive,  and  the  author  of  the  patent 
refrains  from  stating  what  is  necessary  in  order  to  bring  it  about. 
This  process,  which  is  of  little  value,  does  not  deserve  deep  study. 

Dziuk's  Process. — Very  interesting,  however,  is  the  method  of 
Dziuk  (French  patent  No.  286828,  March  15,  1899). 

Dziuk  of  Hanover  uses  the  alkaline-earth  carbides,  as  do  Frank 
and  Caro,  not,  however,  at  the  temperature  of  redness  but  at  that 
of  igneous  fusion  01300-3000°),  the  nitrogen  also  being  previously 


MANUFACTURE   OF  CYANIDES.  151 

heated  at  a  high  temperature.  This  modification  is  based  on  the* 
fact  that  nitrogen  acts  on  the  alkaline-earth  metals  and  on  mag- 
nesium only  at  a  very  high  temperature.  This  fact  led  the  author 
to  believe  that  nitrogen  likewise  should  act  on  the  carbides  only 
at  a  temperature  at  which  their  constituent  elements  are  in  a  free 
or  nascent  state.  And,  in  fact,  he  was  able  to  observe  that  if  a 
current  of  nitrogen,  heated  to  a  high  temperature  before  coming 
in  contact  with  the  carbide,  be  made  to  pass  over  calcium  carbide 
manufactured  in  an  electric  furnace,  this  latter  substance  is  con- 
verted into  cyanide  so  long  as  it  remains  in  the  liquid  state. 

Here  is  how  Dziuk  in  his  patent  explains  this  phenomenon. 
The  nitrogen  is  first  absorbed  by  the  metal  yielding  a  nitride  which 
uniting  with  free  carbon  forms  cyanide. 

In  practice,  Dziuk  uses  any  kind  of  electric  furnaces  which  is 
used  in  the  manufacture  of  carbides.  Into  the  fusion  chamber f 
at  right  angles  to  the  electrodes,  opposite  the  charcoal  tube  enclosing 
the  fusion  mixture,  he  introduces  a  second  charcoal  tube  which 
serves  to  conduct  the  atmospheric  nitrogen  which  has  been  care- 
fully freed  from  carbonic  acid,  moisture,  and  oxygen,  and  which 
has  been  highly  heated. 

Thus,  a  brown-colored  product  is  obtained  which  is  composed 
almost  entirely  of  cyanide  and  contains  but  a  minimum  amount 
of  unconverted  carbide.  It  appears  best  to  allow  the  mass  to  cool 
somewhat  in  the  nitrogenous  atmosphere  of  the  furnace. 

Carbide  in  the  process  of  formation  in  the  electric  furnace  may 
be  used  or  else  carbide  already  formed,  which  however  must  first 
be  subjected  to  fusion.  This  process  is  applicable  to  all  the  alka- 
line-earth carbides  and  to  magnesium  carbide,  likewise  to  a  mix- 
ture of  these  carbides. 

These  gases  which  issue  from  the  furnace  may  be  used  in  heating 
the  nitrogen,  and  the  cyanides  obtained  may  be  converted  into  alkali 
cyanides  by  double  decomposition. 

Dziuk  comes  to  the  same  conclusion  in  an  improvement  to  this 
patent  by  heating  magnesium  or  lime  in  an  electric  furnace  under 
the  action  of  a  current  of  nitrogen,  then  adding  carbon  in  the  form, 
of  coke  in  small  portions.  All  this  without  interrupting  the 
current.  Under  these  conditions  there  is  first  formed  a  nitride 
which  the  carbon  converts  into  cyanide. 


152       METHODS   OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

Process  of  the  General  Electrochemical  Co. — The  last  process 
to  be  mentioned,  which  makes  use  of  carbides,  is  that  of  the  Gen- 
eral Electrochemical  Company  (French  patent  No.  299655,  April  24, 
1900).  Like  Dziuk's  method,  this  process  consists  in  causing  nitrogen 
to  pass  over  carbides  in  an  electric  furnace,  but  with  this  differ- 
<ence  that  the  carbides  are  prepared  in  a  special  manner  so  as  to 
make  them  more  porous,  and  therefore  more  permeable  and  of 
greater  surface  for  the  action  of  nitrogen. 

To  attain  this  state  of  porosity,  coke  is  added  to  the  carbide 
which  renders  it  more  fusible,  or  else  the  carbide  is  prepared  with 
.an  excess  of  carbon. 

In  practice,  the  following  is  the  method  of  procedure:  granu- 
lated carbide  is  mixed  with  coarsely  ground  coke  and  the  mixture 
introduced  into  the  incandescent  electric  furnace.  The  presence 
•of  this  coarse  coke  brings  the  charge  into  a  state  of  porosity  which 
is  very  favorable  to  the  absorption  of  nitrogen.  The  carbides  of 
the  bivalent  elements  are  particularly  suited  to  this  purpose,  for 
they  are  unsaturated  compounds,  each  carbon  atom  having  four 
•chemical  affinities,  two  of  which  may  be  united  to  a  bivalent  alka- 
line-earth metal,  leaving  ^jreg^free  affinities  to  each  carbon  atom. 
With  these  compounds  it  is  quite  easy  to  pass  from  the  unsaturated 
to  the  saturated  state  by  adding  new  elements  having  the  smallest 
number  of  satisfied  affinities.  If  nitrogen  be  passed  through  a 
heated  mass  of  porous  carbide,  each  molecule  of  carbide  absorbs 
two  atoms  of  nitrogen  in  order  to  become  saturated,  the  three  affini- 
ties of  each  carbide  molecule  being  replaced  by  the  three  affinities 
of  each  of  the  two  atoms  of  nitrogen,  it  being  understood  that  car- 
bon has  a  greater  affinity  for  nitrogen  than  for  itself. 

The  best  way  to  obtain  carbide  porous  enough  for  the  manu- 
facture of  cyanides  consists  in  mixing  and  pulverizing  barium 
carbonate  with  an  amount  of  coke  greater  than  that  necessary 
for  the  manufacture  of  barium  carbide.  The  most  convenient 
proportions  to  use  are  3  parts  of  barium  carbonate  and  2  parts  soft 
coal.  This  mixture  is  subjected  to  carboniziation  in  an  ordinary 
retort  furnace.  The  result  is  a  porous  mass  of  coke  in  which  the 
barium  carbonate  is  found  firmly  fixed  to  the  cellular  walls. 

This  mass  is  transferred  to  an  electric  furnace  which  rotates 
-continuously  and  subjected  to  a  sufficient  heat  to  produce  barium 


MANUFACTURE   OF  CYANIDES.  153' 

carbide.  This  substance  fuses  on  to  the  particles  of  coke  present 
in  excess,  forms  a  porous  carbide,  which  afterwards  easily  absorbs 
the  nitrogen  at  a  temperature  below  that  of  the  fusion  of  the  car- 
bide, yielding  a  cyanide  of  barium  which  may  be  separated  by  solu- 
tion and  crystallization. 

Such  are  the  synthetic  processes  which  utilize  atmospheric  nitro- 
gen. As  may  have  been  noticed,  the  progress  achieved  along  this 
line  has  been  remarkable.  Of  all  these  methods,  five  or  six  only 
deserve  to  be  kept  in  mind,  viz.:  those  of  Lambilly,  Margueritte, 
Sourdeval,  Castner,  and  those  of  Frank  and  Caro,  Dziuk,  and  of 
the  General  Electrochemical  Company.  It  is  very  doubtful  if 
the  others  can  be  profitably  exploited. 

B.    PROCESSES   UTILIZING   AMMONIA. 

Nitrogen  being  such  an  inert  element,  and  its  fixation  being 
often  laden  with  difficulties,  it  was  sought  to  utilize  ammonia  whose 
chemical  activities  are  much  greater. 

Liebig  was  one  of  the  first  to  show  that  the  ignition  of  nitroge- 
nous organic  substances  in  the  presence  of  an  alkali  forms  ammonia 
which  in  contact  with  charcoal  heated  to  incandescence  becomes 
converted  into  ammonium  cyanide.  Upon  these  data  are  based 
the  processes  of  Karmrodt,  Lucas,  and  Brunquell  for  the  profitable 
conversion  of  animal  substances  into  cyanides. 

To  Scheele,  however,  belongs  .the  credit  of  having  shown  that 
ammonia  may  contribute  to  the  formation  of  potassium  cyanide. 
Scheele  had  even  invented  a  proce  s  based  on  this  observation  and 
which  consisted  in  heating  a  mixture  of  ammonium  chloride,  char- 
coal, and  potassium  carbonate. 

Somewhat  later  Clouet  demonstrated  that  when  ammonia  was 
passed  over  incandescent  charcoal  a  soluble  substance  was  obtained 
having  a  bitter-almond  taste,  and  which  in  all  probability  was 
ammonium  cyanide,  according  to  the  reaction 


Langlois  likewise  obtained  a  similar  result,  and  noticed  the 
formation  of  small  prismatic  crystals  of  ammonium  cyanide. 

When  a  mixture  of  carbon  monoxid  and  ammonia  was  passed 
over  platinum  sponge  heated  to  redness,  Kuhlmann  likewise  con- 
firmed the  formation  of  ammonium  cyanide. 


154      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

Weltzien  also  obtained  a  similar  result.  All  these  investigations 
are  but  laboratory  experiments,  and  the  investigators  often  found 
themselves  opposed  to  one  another;  nevertheless  to  them  belongs 
the  credit  of  creating  experiments  on  an  industrial  scale.  More- 
over, the  question  is  still  obscure  enough.  In  1897  Bueb  and 
Bergmann  demonstrated  that  when  ammonia  acts  On  incandescent 
charcoal  there  is  formed  not  ammonium  cyanide  but  hydrocyanic 
acid,  according  to  the  equation 

C2+2NH3^2CNH+2H2, 

while  according  to  Lance  (Comptes  Rendus,  April,  1897)  the  prod- 
uct of  this  reaction  is  always  ammonium  cyanide. 

In  the  course  of  his  experiments  on  the  action  of  ammonia  on 
charcoal  at  different  temperatures,  Bueb  showed  that  at  800°  the 
formation  of  hydrocyanic  acid  is  quite  small,  i.e.  about  4%  of  the 
nitrogen  used;  that  at  1000°  the  yield  increases  to  24%,  but  from 
this  temperature  on  the  rest  of  the  ammonia  becomes  dissociated. 

He  noted  that  the  result  was  quite  different  when  a  mixture  of 
ammonia  and  illuminating-gas  was  used  instead  of  ammonia  alone. 
In  that  casb,  even  at  1150-1180°,  three  fifths  of  the  nitrogen  of  the 
.ammonia  are  converted  into  hydrocyanic  acid,  one  fifth  of  the  am- 
monia is  obtained  as  hydrogen  and  nitrogen  from  the  dissociation 
of  the  ammonia,  and  the  remainder  is  not  dissociated. 

Repeating  Bueb's  experiments,  Bergmann  came  to  the  following 
conclusions: 

1.  The  action  of  ammonia  on  charcoal  heated  to  redness  gives, 
indeed,  hydrocyanic  acid,  and  not  ammonium  cyanide. 

2.  The    addition    of   illuminating-gas    to    ammonia    causes    an 
increased  yield  of  hydrocyanic  acid  and  increases  the  resistance  of 
ammonia  to  dissociation. 

By  working  with  a  gaseous  mixture  containing  8-14%  ammonia 
by  volume,  at  a  temperature  between  1100  and  1180°,  Bergmann 
observed  that  19-52%  of  the  nitrogen  was  used  and  converted  into 
hydrocyanic  acid,  69.2  to  19%  was  found  in  the  state  of  ammonia, 
and  11  to  41%  as  free  nitrogen.  Moreover,  the  yield  varies  in 
inverse  ratio  to  the  velocity  of  the  gases. 

3.  If,  instead  of  illuminating-gas,  hydrocarbons  of  higher  molecular 
weights  be  used,  the  yield  of  hydrocyanic  acid  is  not  increased  but 


MANUFACTURE  OF  CYANIDES. 


155 


rather  diminished,  which  fact  seems  to  prove  that  nascent  carbon 
has  no  action  on  ammonia. 

4.  If  the  illuminating-gas  be  replaced  by  carbon  monoxid,  the 
yield  is  about  the  same,  but  the  amount  of  dissociated  ammonia 
is  greater. 

Below  are  the  results  obtained  by  Bergmann. 


Duration  of 
Experiment. 

Temperature. 

Per  Cent  NH3 
by  Volume. 

Per  Cent  of  N 
used  in  Form 
of  CNH. 

hr.   niiu. 

1      — 

1130 

46 

28.1 

1      — 

1020 

37 

33.4 

1     20 

1100 

17 

39.9 

1     — 

1100 

17 

42.0 

50 

1130 

17 

39.5 

33 

1130 

17 

36.2 

1     35 

1130 

10 

44.2 

45 

1100 

8 

56.4 

1       6 

1100 

5 

43.7 

5.  The   increase  in  the    yield  of   hydrocyanic  acid,  confirmed 
in  the  experiments  made  with  mixtures  of  ammonia  and  carbon 
monoxid  or  illuminating-gas,  is  not   due  to  the  chemical  action 
exerted  by  this  gas,  as  one  would  be  led  to  believe,  according  to 
the  equation 

CO+NH3  =  CNH+H20, 

but  it  is  the  result  only  of  the  dilution  of  the  ammonia-gas.  In 
fact,  in  many  experiments  made  with  carbon  monoxid  and  ammonia 
without  the  intermediary  of  wood  charcoal,  Bergmann  proved 
that  only  0.4  to  0.6%  of  the  nitrogen  used  in  the  form  of  ammonia 
wac  converted  into  hydrocyanic  acid,  32.5-62.2%  was  found  as 
ammonia,  and  34-68%  in  the  form  of  free  nitrogen. 

6.  The  most  favorable  temperature  for  the  formation  of  hydro- 
cyanic acid  depends  materially  on  the  nature  of  the  gases  used  in 
diluting  the  ammonia.    It  is  from  1000  to  1100°  for  carbon  monoxid, 
generator  gases,  and  mixtures  of  hydrogen  and  nitrogen;  1100°  at 
least  for  the  various  gaseous  hydrocarbons.     At  this  temperature 
the  dissociation  of  the  ammonia  decreases  as  the  molecular  weights 
of  the  hydrocarbon  increases. 


156       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

Compared  with  the  results  of  Bergmann  those  of  Lance  present 
Striking  analogies,  while  at  the  same  time  differing  considerably. 

While  studying  the  action  of  ammonia-gas  on  charcoal  heated 
to  redness,  Lance  observed  (Comptes  Rendus,  April,  1897)  that 
if  dry  ammonia-gas  be  passed  over  wood  charcoal  at  the  rate  of 
four  liters  per  hour,  at  a  temperature  between  1000  and  1100°, 
(1)  ammonium  cyanide  is  always  formed;  (2)  the  yield  is  great- 
est at  this  temperature;  (3)  the  nitrogen  combined  under  this 
form  is  equal  to  25%  of  the  nitrogen  used  under  the  form  of 
ammonia. 

If  the  ammonia-gas  be  diluted  with  hydrogen  and  nitrogen,  the 
results  are  quite  different. 

1.  If  the  ammonia  constitutes  I/Q  of  the  gaseous  mixture,  the 
yield  in  nitrogen  converted  into  cyanogen  in  increased  to  30.6%. 

2.  This  yield  increases  with  the  increase  of  the  quantiy  of  hydro- 
gen in  relation  to  the  nitrogen,  and  may  react  89.66%  if  the  nitrogen 
constitutes  but  1/io  of  the  volume  of  hydrogen. 

3.  Under  these  conditions  at  least  70%  of  the  nitrogen  of  the 
ammonium  cyanide  comes  from  the  free  nitrogen  of  the  mixture,  i.e., 
from  the  nitrogen  of  the  air. 

From  these  results,  which  are  similar  and  yet  contradictory, 
the  conclusion  reached  is  that  the  action  of  ammonia-gas  alone, 
or  mixed  with  other  gases,  on  incandescent  charcoal,  is  not  at  all 
well  known.  It  requires  still  considerable  study.  Probably  the 
action  of  the  carbon  is  only  one  of  contact,  as  is  the  case  in  many 
chemical  reactions.  This  hypothesis  is  all  the  more  probable  if 
one  recalls  how  Bergmann  was  able  to  obtain  only  traces  of  cyanogen 
by  the  action  of  nitrogen  on  carbon  monoxid  in  the  absence  of  char- 
coal, and,  on  the  other  hand,  Kuhlmann  obtained  appreciable  quan- 
tities of  ammonium  cyanide  by  working  with  the  same  gases,  but 
in  the  presence  of  platinum  sponge  heated  to  redness.  Be  that 
as  it  may,  these  investigations  have  been  the  point  of  departure 
of  several  processes  based  on  the  action  of  ammonia  upon  incan- 
descent wood  charcoal. 

Lance  and  Bourgade's  Process. — First  comes  the  method  of  Lance 
and  Bourgade  (French  patent  No.  265932,  1897).  In  this  process 
ammonia  is  used  only  as  the  carrier  of  hydrogen  and  nitrogen.  Under 
the  name  hydrogen  the  authors  mean  all  the  gaseous  hydrocarbons, 


MANUFACTURE  OF  CYANIDES.  157 

gas,  water,  etc.,  and  by  nitrogen  is  meant  either  pure  nitrogen  or 
in  the  form  of  mixtures,  such  as  air  and  the  products  of  combustion 
of  manufacturing  establishments. 

This  process  is  based  on  the  following  reactions:  If  a  mixture 
of  acetylene  and  nitrogen  be  made  to  act  upon  one  another  in  the 
presence  of  intense  heat,  there  is  formed  hydrocyanic  acid.  The 
richer  the  mixture  is  in  hydrogen,  the  nearer  to  the  theoretical 
yield  is  the  amount  of  hydrocyanic  acid.  It  is  at  a  maximum  when 
the  volume  of  hydrogen  is  at  least  two  and  one  half  times  that  of 
the  hydrogen  combined  in  acetylene. 

If  therefore  a  mixture  of  nitrogen,  hydrogen,  and  ammonia  be 
passed  over  carbon,  there  is  formed  an  acetylene  carbide  of  ammo- 
nium, C4(NH4)2,  which  is  only  a  transition  product  with  which  free 
nitrogen  combines,  yielding  the  compound  C2N-NH4  or  ammonium 
cyanide  : 

2NH3+2H+4C  = 


C4(NH4)2+2N=2(C2N.NH4). 

The  yield  approaches  the  theory  in  proportion  as  the  conditions 
stated  above  relative  to  the  mixture  of  the  three  gases,  nitrogen, 
hydrogen,  and  ammonia,  are  adhered  to.  In  their  German  patent 
No.  100775,  taken  Aug.  22,  1897,  Lance  and  Bourgade  give  the 
following  proportions  : 

Ammonia-gas  ...........................       80  liters 

Hydrocarbon  ...........................   2000     '  ' 

Nitrogen  of  air  ..........................     200    '  ' 

The  ammonium  cyanide  obtained  is  then  treated  by  well-known 
and  appropriate  methods  to  convert  it  into  alkali  cyanide. 

Mactear's  Process.—  This  is  a  somewhat  similar  process  (U.  S. 
patent  No.  654466,  July  24,  1900,  French  patent  No.  292639).  It 
consists  in  passing  a  mixture  of  carbon  monoxid  and  ammonia-gas 
through  a  specially  constructed  chamber  filled  with  wood  char- 
coal or  other  suitable  catalytic  substance  heated  to  1800-2000° 
by  means  of  electrical  resistances. 

The  mixture  of  the  two  gases  is  previously  made  in  a  closed 
chamber  in  the  proportion  of  two  volumes  of  ammonia-gas  and 


158       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

one  volume  carbon  monoxid.  This  gaseous  mixture  is  then  con- 
ducted through  the  decomposition  chamber.  The  carbon  monoxid 
should  be  pure;  it  is  produced  by  passing  a  current  of  carbonic 
acid  over  coke  heated  to  redness.  The  ammonia  is  obtained  by 
the  decomposition  of  ammonium  sulphate  with  lime. 

The  gaseous  products  consist,  for  the  most  part,  of  ammonium 
cyanide.  This  latter  product  is  then  converted  into  alkali  cyanide 
by  treating  it  with  a  corresponding  amount  of  alkali  hydrate  in 
a  water  or  alcoholic  solution. 

The  ammonia  of  the  ammonium  cyanide  is  set  free  and  collected 
the  solution  of  alkali  cyanide  is  then  evaporated. 

Process  of  the  Stassfurter  Chemische  Fabrik.  —  This  process 
belongs  to  that  class  which  utilizes  the  reaction  of  ammonia  on 
charcoal.  It  is  based  on  the  following  facts:  When  a  current  of 
ammonia  is  passed  over  a  mixture  of  alkali  or  alkali  carbonate  and 
charcoal  heated  to  dull  redness,  there  is  formed,  indeed,  a  cyanide, 
but  only  in  small  amount,  whereas  a  considerable  amount  of  cyanate 
is  produced. 

The  result  is  quite  otherwise  if  the  ammonia-gas  be  conducted 
through  at  a  dull-red  heat,  and  if  after  this  adduction  has  ceased 
the  heat  is  increased  to  full  redness;  the  cyanate  at  first  formed 
is  reduced  to  alkali  cyanide. 

Gruneberg,  Flemming,  and  Siepermann  have  patented  a  cyanide 
furnace  (German  patents  Nos.  38012, 1886;  51562,  1889;  French  pat- 
ent No.  200492,  1889)  which  has  precisely  the  object  of  utilizing 
these  reactions. 

The  manufacture  of  cyanide  takes  place  in  two  stages  in  vertical 
retorts,  several  of  which  are  placed  in  the  furnace  and  comprising 
many  parts;  one  part  is  heated  to  dull  redness  where  the  cyanate 
is  formed,  the  other  part  heated  to  full  redness  where  the  cyanate 
is  reduced  to  cyanide. 

These  retorts,  A  (Figs.  6  and  7),  are  enclosed  in  the  furnace  B 
with  flues  and  placed  in  such  a  manner  that  the  lower  part  of  them 
is  heated  to  an  intense  red,  while  the  upper  part  is  heated  to  a  dull 
red.  The  lowest  part  of  the  retorts,  C,  is  situated  outside  the  fur- 
nace. It  serves  as  a  cooler  for  the  cyanide  formed,  which  is  then 
collected  in  the  receiver  D,  whence  it  is  carried  off  by  an  endless 
canvas  E.  The  mass,  which  is  to  be  converted  into  cyanide,  com- 


MANUFACTURE  OF  CYANIDES. 


159 


posed  of  bits  of  wood  charcoal  impregnated  with  potassium  car- 
bonate ,  falls  in  virtue  of  its  own  weight  from  that  part  the  least 
heated  into  that  part  which  is  heated  to  intense  redness.  It  is 
introduced  through  the  hoppers  FF,  which  are  afterward  closed. 


FIG.  6. — Apparatus  of  the  Stassfurter  Chemische  Fabrik 

As  soon  as  the  desired  temperature  has  been  reached,  the  tube  G 
is  pushed  so  as  to  bring  about  the  lower  opening  at  the  point  where 
the  dull-red  zone  begins. 

Then  a  carefully  regulated  current  of  ammonia  is  allowed  to 


160       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

pass  through.  The  products  of  the  reaction  fall  slowly  into  the 
receiver  D  and  are  carried  off  by  the  endless  canvas  E.  The  hop- 
per F  is  filled  at  regular  intervals.  The  gases,  set  free  during  the 
reaction,  go  out  through  the  tube  H,  in  whose  axis  is  the  tube  G  con- 
ducting the  ammonia.  A  revolving  drum,  J,  situated  in  the  lateral 
flues  of  the  furnace  and  heated  by  the  flames  escaping  from  the 
latter,  permits  the  charge  to  be  dried  beforehand,  for  it  should  not 
be  used  in  a  moist  state.  The  mass  obtained  is  systematically 
treated  with  water  until  the  solutions  show  a  specific  gravity  of 
40°  B.  The  liquor  is  then  treated  with  carbonate  of  potash  either 


FIG.  7. — Apparatus  of  the  Stassfurter  Chemische  Fabrik. 

at  ordinary  or  at  a  higher  temperature.  The  greater  portion  of 
the  potassium  cyanide  separates  immediately  if  the  work  be  carried 
on  at  ordinary  temperatures,  or  crystallizes  on  cooling  if  carried 
on  at  a  higher  temperature. 

The  Stassfurter  Chemische  Fabrik,  formerly  Forster  &  Grune- 
berg,  which  has  installed  this  process  in  its  works,  has  at  the 
present  time  52  such  furnaces,  *  which  are  regularly  operated, 
and  which,  it  seems,  give  splendid  results.  It  would  appear  that 
negotiations  were  in  progress  last  year  between  a  French  com- 
pany and  the  German  company  for  the  installation  of  this  process 
in  a  chemical  works  near  Paris. 

Moulis  and  Sar's  Process. — This  process  (French  patent  No. 
265715,  March  26, 1897)  likewise  makes  use  of  the  action  of  ammo- 
nia on  charcoal.  The  necessary  ammonia  is  produced  from  the 
nitrogen  of  the  air  in  the  following  way: 


MANUFACTURE  OF  CYANIDES.  161 

Air  under  pressure  is  blown  into  a  vat-like  furnace  containing 
a  certain  quantity  of  small  pieces  of  wood  charcoal  or  cinders  of 
coke.  First  there  is  formed  carbonic  acid,  which  passing  through 
the  red-hot  charcoal  of  the  upper  zone  is  converted  into  carbon 
monoxid.  This  oxid  of  carbon,  together  with  a  small  amount  of 
carbonic  acid  and  undecomposed  air,  passes  before  a  reservoir  of 
air  so  placed  that  this  air  becomes  thoroughly  mixed  with  the  oxid 
of  carbon  so  as  to  produce  its  complete  combustion.  In  this  way 
a  mixture  of  nitrogen  and  carbonic  acid  is  obtained  together  with 
a  considerable  amount  of  calories  which  may  be  used  in  heating 
the  apparatus.  The  carbonic  acid  is  absorbed  by  potash  or  sodium 
hydroxide  and  the  nitrogen  stored  in  a  gasometer. 

On  the  other  hand,  hydrogen  is  produced  according  to  well- 
known  methods  (zinc  and  acid  of  20°  B.).  When  this  hydrogen 
passes  through  nitrogen,  at  suitable  temperatures,  ammonia  is 
formed.  This  latter  gas  passes  through  a  refractory  tube  heated 
by  means  of  oxid  of  carbon,  and  into  which  dehydrated  and  liquefied 
tar  flows.  Under  these  conditions  the  tar  is  vaporized,  the  vapors 
coming  in  contact  with  the  ammonia  and  forming  ammonium  cya- 
nide, which  is  collected  in  water  and  afterward  converted  into  alkali 
cyanide. 

The  action  of  ammonia  (substituted  for  nitrogen)  on  the  oxids^ 
carbonates,  and  metals  of  the  alkalis,  in  the  presence  of  charcoal, 
has  likewise  been  tried.  The  processes  of  this  kind  are  quite  numer- 
ous and  will  now  be  passed  in  review. 

Lambilly's  Process. — Lambilly,  whose  remarkable  researches 
have  been  discussed  at  the  beginning  of  this  chapter,  is  one  of 
the  first  to  have  tried,  with  some  success,  to  replace  nitrogen, 
either  partly  or  wholly,  by  ammonia.  Having  remarked  that  the 
reactions  were  conducted  with  greater  ease  if  the  carbon  was  in 
the  nascent  state,  Lambilly  thought  that  this  advantage  would 
be  still  more  manifest  if  the  nitrogen  also  was  in  this  state,  and 
with  this  end  in  view  he  proposed  to  substitute,  partially  or  wholly, 
the  nitrogen  with  ammonia.  In  his  French  patent  (No.  223868, 
Aug.  26,  1892)  he  works  as  follows:  He  uses  a  mixture  of  hydro- 
carbon-gas and  ammonia-gas  with  the  optional  addition  of  free 
nitrogen.  This  mixture  is  decomposed  at  a  high  temperature  in 
the  presence  of  an  alkali  or  alkaline-earth  compound  and  charcoal. 


162       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

The  cyaniding  mixture  is  obtained  in  the  following  way:  A  con- 
centrated solution  of  carbonate  of  potash  or  caustic  potash  or  caustic 
Boda  is  made,  into  which  is  poured  pulverized  charcoal  at  the  rate 
of  100  parts  per  each  100  parts  alkali.  This  mixture  is  evaporated  to 
dryness,  then  to  it  are  added  20-30  parts  powdered  lime  and  50  parts 
iron  filings,  and  the  whole  is  massed  together  into  the  form  of  bri- 
quettes with  the  aid  of  tar  or  other  like  substance.  These  are  then 
ignited  in  iron  retorts  or  cylinders  heated  to  bright  redness  in 
such  a  way  as  to  reduce  as  much  as  possible  the  alkali  compound 
and  to  convert  it  into  a  state  favorable  for  the  absorption  of  nitrogen. 
This  operation  is  best  carried  on  in  a  vacuum.  When  this  is  fin- 
ished, this  point  being  indicated  by  the  cessation  of  the  liberation 
of  gas  (H20  or  C02)  according  to  the  alkali  compound  (hydrate 
or  carbonate)  used,  the  gaseous  mixture  of  ammonia  and  hydro- 
carbon with  or  without  free  nitrogen  is  made  to  pass  through. 
The  latter  gas  is  produced  by  passing  air  over  copper  heated  to 
redness,  and  the  oxid  of  copper  formed  serves  in  carbureting  the 
hydrocarbon-gas.  This  hydrocarbon-gas  should  preferably  be  quite 
dense.  It  may  be  profitably  obtained  by  heating  charcoal  impreg- 
nated with  heavy  coal-tar  oil  in  cylinders  at  a  temperature  between 
50  and  300°. 

The  gaseous  mixture  passes  over  the  cyaniding  substances  under 
a  slight  pressure,  in  order  to  bring  it  into  intimate  contact  with 
all  the  particles  of  this  substance.  On  issuing  from  the  retorts  the 
gases  are  recarbureted.  The  mass  so  obtained  is  withdrawn  from 
the  cylinder  and  treated  with  water.  In  the  claims  of  his  patent 
Lambilly  states  the  following  advantages  of  his  process: 

1.  A  great  rapidity. 

2.  It    permits,  in  a  single  operation   in  a  definite  amount  of 
alkali,  the  amassing  of  more  cyanide  than  any  other  process  at 
the  time  known. 

3.  It  is  therefore  very  economical. 

Beilby's  Process. — This  process,  dating  from  the  same  year 
(French  patent  No.  219156,  Feb.  4,  1892),  does  not  present  any  great 
improvement  over  the  processes  then  known,  and  besides  the  net 
cost  must  be  quite  high.  It  consists  in  passing  a  current  of  ammonia 
through  a  melted  mixture  of  anhydrous  caustic  alkali,  cyanides^ 
and  finely  powdered  charcoal  heated  at  a  high  temperature  in  a 


MANUFACTURE   OF  CYANIDES.  163 

suitable  apparatus.     The  addition  of  cyanide  is  to  lower  the  point 
of  fusion  of  the  mass,  in  order  to  avoid  deterioration  of  the  iron 
receptacles  in  which  the  operation  is  conducted. 
The  amounts  stated  by  Beilby  are: 

Pulverized  charcoal 20  to  25% 

Potassium  carbonate 55  "  60% 

Potassium  cyanide 20% 

The  apparatus  used  are  retorts  or  pots  of  iron  provided  with 
a  tube  for  the  inlet  of  ammonia,  an  outlet  tube,  a  hopper,  and  a  tap- 
hole. 

The  ammonia  may  bubble  through  the  melted  mixture,  or  else 
the  mixture  may  be  subjected  to  an  energetic  stirring  by  means 
of  a  mechanical  stirrer  during  the  passage  of  the  current  of  am- 
monia. 

It  is  important  always  to  have  some  potassium  cyanide  in  the 
mixture  during  the  operation,  and  in  such  amount  that  the  mass 
remains  fluid,  without,  however,  producing  foam,  which  might 
obstruct  the  exit. 

The  cyanide  which  in  part  is  volatilized  is  collected  in  a  system 
of  condensers.  The  operation  may  be  so  conducted  that  the  whole 
of  the  cyanide  is  volatilized.  Ammonia  may  be  substituted  by 
the  alkaloid  bases  of  the  pyridine  series. 

As  was  remarked,  this  method  must  be  rather  expensive  because 
of  the  amount,  1/5,  of  cyanide  added  to  the  other  products. 

The  substitution  of  the  alkaloid  bases  for  the  ammonia  is  not 
profitable.  Besid  s  being  expensive  bodies,  they  are  quite  resistant 
to  high  temperatures  and  an  appreciable  amount  of  these  bodies 
thus  escape  decomposition,. 

Young  and  Macfarlane's  Process. — The  method  of  Barr,  Mac- 
farlane,  Mills,  and  Young  (English  patent  No.  3092,  1892;  French 
patent  No.  230066,  May  13,  1893)  is  somewhat  different.  It  is  based 
on  the  action  of  a  mixture  of  ammonia  and  carbon  monoxide  on  a 
fused  mixture  of  alkali  hydrate  or  carbonate  and  charcoal,  accord- 
ing to  the  general  reactions: 


164   METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS 


H-CO-NH2  = 
2CNH  +  C03K2  +  C  =  2CNK  +  H20  +  2CO. 

The  most  suitable  proportions  are: 

Caustic  potash  ......  ...................  100.0  parts 

Charcoal  (wood  charcoal  or  coke)  .........    22.5    " 

This  mixture  is  heated  at  815°  C.  in  a  retort  or  other  receptacle, 
then  a  current  of  carbon  monoxid  and  ammonia  is  passed  through, 
either  separately  or  previously  mixed,  and  heated  if  thought  necessary. 
Under  these  conditions  there  is  formed  a  cyanide  corresponding 
to  the  base  used,  which  may  afterward  be  separated  and  purified 
according  to  ordinary  methods.  The  gases  which  come  out  of 
the  retorts  may  be  used  over  again  after  being  enriched  with  the 
one  or  other  necessary  constituent. 

As  a  profitable  source  of  ammonia  and  carbon  monoxid,  the 
authors  recommend  using  the  gases  of  blast-furnaces  or  other  indus- 
trial furnace  gases,  likewise  gases  from  slate-retorts  or  from  gas- 
works, after  purification,  if  they  are  thought  suitable. 

Under  these  conditions  the  authors  claim  a  yield  of  70%.  Repeat- 
ing the  experiments  of  Young  and  Macfarlane  under  the  most  favor- 
able conditions,  Conroy  was  able  to  obtain  a  yield  of  but  30%.  He 
remarked,  besides,  that  the  cyanide  is  formed  very  slowly,  Mac- 
farlane himself  has,  moreover,  stated  that  36  hours  are  required 
to  produce  a  yield  of  potassium  cyanide  of  from  60-70%.  The 
longer  the  experiment  continues,  the  more  rapid  becomes  the  for- 
mation of  cyanide.  This  method,  moreover,  requires  an  elevated 
temperature,  which  causes  a  rapid  wear  and  tear  of  the  apparatus. 
Thus,  in  Young  and  Macfarlane's  experiments,  the  steel  tube  which 
was  used  in  carrying  on  the  reaction  was  reduced,  at  the  end  of 
36  hours,  to  the  thickness  of  an  ordinary  sheet  of  paper.  Conroy 
repeated  the  experiment  with  a  cast-iron  tube  and  noted  a  similar 
wear.  According  to  him  the  reaction  would  take  place  as  follows: 


NH3+KOH=KNH2 
KNH2  +  CO  =  CNK  +  H20. 


MANUFACTURE  OF  CYANIDES.  165 

According  to  the  authors  of  the  patent  there  would  be  formed 
formamide,  which  would  then  break  up  into  water  and  hydrocyanic 
acid,  which  latter  would  be  absorbed  by  an  alkali. 

Conroy's  hypothesis  presupposes  the  formation  not  of  formamide, 
but  of  potassamide.  According  to  his  idea,  the  formation  of  cyanide 
is  due  rather  to  a  simultaneous  action  of  the  three  substances  pres- 
ent, and  probably  with  the  formation  of  potassamide  as  an  inter- 
mediary product.  Moreover,  Beilsten  and  Geuther  had  previously 
established  the  fact  that  the  oxid  of  carbon  reacts  on  the  potassa- 
mide with  formation  of  potassium  cyanide.  Repeating  this  experi- 
ment by  heating  potassamide  in  a  glass  tube  at  50-600°  under  the 
action  of  a  current  of  carbon  monoxid,  Conroy  was  able  to  obtain  a 
yield  of  35%  potassium  cyanide.  He  considered,  however,  that 
if  instead  of  a  glass  tube  he  had  used  an  iron  tube,  the  yield  would 
have  been  almost  theoretical.  Without  deciding  in  favor  of  either 
one  or  the  other  of  these  two  suppositions,  both  equally  established, 
it  will  be  seen  further  on  that  the  latter  seems  more  probable,  judg- 
ing from  the  results  recently  obtained  with  a  new  process  the  object 
of  which  is  the  intermediary  production  of  alkali  amides.  Never- 
theless, since  these  data  have  not  yet  been  confirmed  experimentally 
we  will  rely  on  the  results  obtained. 

Chaster 's  Process. — This  process  (1894)  does  not  present  any- 
thing very  new  or  characteristic.  It  simply  consists  in  passing 
ammonia  which  has  been  previously  dried  over  quicklime,  over 
an  intimate  mixture  of  coal  and  a  carbonate  of  an  alkali  or  alka- 
line earth.  As  in  Lambilly's  process,  this  mixture  is  prepared  by 
adding  powdered  coal  to  a  concentrated  solution  of  carbonate, 
evaporating  to  dryness,  and  igniting. 

Pleger's  Process. — This  process  (German  patent,  No.  89594,  Aug. 
7,  1895)  also  does  not  differ  much  from  the  preceding  ones.  It 
consists  likewise  in  causing  a  current  of  ammonia  to  act  on  a  mix- 
ture of  alkali  and  charcoal  heated  to  900°.  The  author,  however, 
does  not  add  at  once  the  whole  of  the  charcoal  necessary.  Only 
a  portion  of  it  is  used,  the  rest  being  carried  in  gradually  with  the 
ammonia-gas  which  is  blown  into  the  crucible.  Ammonia  charged 
with  pulverized  charcoal  is  continually  blown  in  until  there  is  no 
longer  any  liberation  of  hydrogen  or  of  carbon  monoxid.  When 
this  point  has  been  reached  the  mass  is  allowed  to  remain  in  quiet 


166       METHODS  OF  MANUFACTURING  CYANIDE   COMPOUNDS. 

I  fusion,  and  the  melted  cyanide  is  filtered  in  order  to  separate  it 
|  from  the  excess  of  charcoal.  As  in  all  the  preceding  processes  of 
I  this  class,  the  ammonia  may  be  replaced  by  nitrogen,  either  of  the 
[  air  or  in  the  form  of  the  mixture  which  the  local  combustion  of 
1  carbon  in  excess  produces. 

These  various  processes,  which  are  more  or  less  similar,  pro- 
duce greater  or  Jess  amounts  of  cyanide,  the  yield,  however,  never 
being  equal  to  the  theoretical,  and  Conroy  estimates,  and  not  with- 
out reason,  that  2/3  are  lost.  One  of  the  causes  of  this  failure  is 
to  be  found  in  the  resistance  which  the  cyaniding  mixture  presents 
to  the  action  of  ammonia-gas.  Now,  one  of  the  essential  condi- 
tions of  success  is  that  the  mixture  allow  the  gaseous  current  to- 
circulate  freely  while  being  intimately  penetrated  by  it. 

Roca's  Process. — Roca  in  his  French  patent  No.  266550,  May  3, 
1897,  seems  to  have  realized  this  desideratum.  For  this  purpose 
he  first  brings  his  cyaniding  mixture  to  a  special  physical  condition 
of  porosity,  which  is  especially  suited  to  assure  the  most  perfect 
and  most  economical  absorption  and  circulation  of  the  ammonia 
throughout  the  mixture  and  its  transformation  proceeds  into 
cyanide. 

Roca  starts  with  the  idea  that  this  mixture  should  not  be  so 
fine  as  dust,  but  rather  in  small  pieces  which  will  leave  spaces  between 
each  other  large  enough  to  allow  the  circulation  of  the  gas  and 
permeable  enough  to  this  gas  that  the  action  will  not  be  confined 
to  the  surface.  Moreover  their  weight  should  not  be  such  as  to 
cause  the  pieces  to  become  crushed,  and  therefore  they  should  main- 
tain a  certain  degree  of  hardness. 

Toward  this  end  he  mixes  finely  ground  wood  charcoal,  ground 
in  the  presence  of  water  so  as  to  lay  the  excessive  dust,  with  the 
purest  commercial  potassium  carbonate  in  the  proportion  of  30-35 
parts  of  charcoal  t,o  65-75  parts  carbonate.'  He  adds  10-20%  water 
so  as  to  make  the  mass  homogeneous  and  slightly  moist.  Thus 
prepared,  this  mixture  when  squeezed  in  the  hand  should  form 
a  soft  ball. 

This  mass  is  then  spread  out  and  pressed  into  thin  layers  upon 
a  metallic  floor  capable  of  being  heated.  The  potassium  carbonate 
dissolves  in  the  small  amount  of  water  contained  in  the  mixture  and 
then  it  imbibes  the  charcoal,  the  whole  forming  an  intimate  mass. 


MANUFACTURE   OF  CYANIDES.  167 

The  mass  then  becomes  turgid  and  coherent,  and  under  the  influence 
of  heat  the  small  quantities  of  air  and  water-vapor  seek  to  escape, 
leaving  small  cavities  in  the  interior  of  the  mass.  Finally,  after 
drying  completely,  there  is  obtained  a  sufficiently  hard  charcoal,, 
which  resists  being  crushed,  which  is  very  homogeneous,  porous, 
and  at  the  same  time  of  very  low  specific  gravity  (density  0.45— 
0.55),  and  which  may  be  cut  up  into  briquettes.  This  mass  is  kept 
out  of  contact  of  air  and  moisture  until  it  is  to  be  used. 

This  mass  is  charged  into  vertical  cast-iron  retorts  which  are 
hermetically  covered  and  provided  at  the  lower  part  with  a  vane, 
forming  an  air-tight  joint  during  the  cyaniding  process.  It  is  only 
necessary  to  open  this  vane  to  make  the  cyanided  product  flow  into 
a  sheet-iron  extinguisher. 

These  retorts  are  arranged  in  series  of  five  or  six  in  suitable 
furnaces.  Each  retort  is  provided  with  two  tubulatures.  One, 
placed  near  the  cover,  serves  to  admit  the  gases;  the  other,  placed 
a  little  above  the  vane,  serves  as  their  exit.  The  bottom  of  the 
retorts  are  covered  with  pieces  of  dry  wood  charcoal  so  arranged 
as  to  avoid  any  incomplete  transformation  on  account  of  lack  of 
heat  and  to  facilitate  the  exit  of  gases. 

Uniform  circulation  and  continuity  of  working  are  made  sure 
by  a  system  of  pipes  and  suitable  valves  (see  Fig.  8). 

The  arrangement  shown  in  Fig.  8  permits  one  to  understand  the 
principle  of  the  apparatus  and  the  workings  of  the  various  taps. 
According  to  the  cut,  ammonia-gas  is  admitted  into  the  apparatus 
by  way  of  tap  73  in  the  retort  C3,  which  is  the  one  earliest  charged; 
it  passes  into  retort  C2  by  means  of  Z2,  and  into  retort  d  through 
XL  From  this  retort  the  gas  goes  through  the  tap  X5  into  <75, 
and  through  X4  into  C4;  then  it  flows  into  the  exit  tube  through 
the  tap  F4.  Every  time  a  retort  is  cyanided,  the  order  of  using 
the  cocks  is  changed  and  thus  a  continuous  operation  is  permitted. 
By  means  of  this  arrangement  any  one  of  the  retorts  may  be  dis- 
connected during  the  unloading  and  reloading  without  stopping 
the  operation  in  the  other  retorts. 

In  this  way  a  mixture  of  nearly  pure  cyanide  and  charcoal  is 
obtained  which,  after  cooling,  may  be  treated  with  water  and  puri- 
fied in  the  usual  way.  The  residual  charcoal,  when  well  washed, 
may  be  used  anew. 


168      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

The  gases  which  are  discharged  from  the  furnace  are  cooled 
and  are  then  conducted  into  a  tower  filled  with  coke,  where  a  thin 
stream  of  water  circulates  and  holds  back  the  entrained  ammonia. 
Thence  they  are  conducted  under  the  hearth  and  used  as  fuel,  for 
they  liberate  more  heat  than  is  absorbed  by  the  endothermic  reac- 
tion obtained  in  the  retorts.  In  this  way  the  expense  of  fuel  is 
considerably  lessened,  and  in  fact  it  is,  on  this  account,  very  small. 


Tnlet  for  Ammonia- 


Qutlet-tor  Gas 


FIG.  8. — Roca's  Apparatus  (plan). 

In  an  addition  to  his  patent,  Roca  advises  the  substitution  of 
barium  carbonate  instead  of  potassium  carbonate,  and  this  for  several 
reasons. 

The  cyanide  obtained  is  very  soluble  and  chemically  pure,  the 
barium  carbonate  being  insoluble  and  not  passing  into  the  cyanide 
solution  when  the  cyanide  is  treated  with  water. 

Barium  carbonate  is  not  so  expensive  and  it  may  be  regenerated 
when  the  barium  cyanide  is  converted  into  alkali  cyanide.  More- 
over, at  the  temperature  at  which  the  reaction  takes  place  (800- 
900°),  carbonate  of  barium  dissociates  much  less  than  does  carbo- 
nate of  potassium,  and  almost  no  soluble  baryte  is  formed  to  con- 
taminate the  cyanide. 

The  cyaniding  mixture  is  formed  by  mixing  100  parts  of  the 


MANUFACTURE  OF  CYANIDES. 

purest  commercial  carbonate  of  barium  with  30-35  parts  wood  char- 
coal. Then  are  added  20-25  parts  of  a  dilute  and  warm  solution 
of  gelatine  in  order  to  make  the  mixture  cohere.  After  drying, 
the  mixture  is  broken  up  into  pieces  of  the  desired  size,  and  these 
are  transferred  to  the  apparatus  described  above  and  treated  in  the 
same  manner. 

The  product  thus  obtained  is  treated  with  water,  and  after  fil- 
tration the  barium  cyanide  is  converted  into  an  alkali  cyanide 
by  the  addition  of  an  alkali  carbonate  according  to  the  following 
reaction : 

(CN)2Ba+C03K2   or  C03Na2=C03Ba+2CNK   or   2CNNa. 

soluble  soluble  insoluble  soluble 

The  precipitated  barium  carbonate  is  separated  by  filtration, 
and  after  drying,  it  may  be  used  anew. 

As  may  be  seen,  Roca's  process  is  really  ingenious,  and  it  shows 
a  marked  improvement  over  all  the  preceding  processes.  Yet  it  is 
very  doubtful  if  by  this  process,  even,  a  theoretical  yield  can  be 
obtained,  a  condition  which  is  extremely  difficult  of  fulfilment  when 
the  oxids  or  carbonates  of  the  alkalis  are  used. 

Hood  and  Salomon's  Process. — Before  taking  up  the  study  of 
processes  working  directly  on  the  alkali  metals  themselves,  which 
to  our  mind  simplifies  the  solution  of  the  problem  very  much,  we 
cannot  omit  mentioning  the  very  original  and  peculiar  process  of 
Hood  and  Salamon  (German  patent  No.  15142,  1895-1896). 

This  process  differs  from  the  preceding  in  that  it  is  worked  not 
in  the  dry  way  but  in  the  wet  way.  In  an  early  patent  (English 
patent  No.  87613,  Sept.  4,  1894)  Hood  and  Salamon  worked  in  the 
dry  way.  The  alkali  carbonate  was  treated  with  a  reducing  metal 
— zinc,  lead,  etc. — and  this  mixture  was  heated  to  redness  in  a  cur- 
rent of  dry  ammonia.  The  reaction  is  as  follows: 

NH3  +  C03Na2 + Zn = CNNa + NaOH + ZnO + H2O, 

but  only  half  of  the  alkali  metal  is  converted  into  cyanide.  In 
order  to  complete  the  reaction  profitably  the  authors  proposed 
that  a  current  of  heated  carbonic  acid  and  ammonia  be  passed 


170       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

over  the  mixture,  or  that  a  bit  of  charcoal  be  added  to  the  mass 
in  order  to  reduce  the  cyanate  formed  as  well  as  the  oxid  of 
zinc. 


2Zn+C02, 
2NaOH+C02  =C03Na2+H20. 

In  the  German  patent  (No.  15142,  1895-1896)  Hood  and  Sal- 
amon  operate  in  the  wet  way.  If  metallic  zinc  be  in  suspension  in 
strong  alkaline  solutions  to  which  carbonates  or  bicarbonates  have 
been  added,  and  a  current  of  ammonia  be  passed  through  these 
boiling  lyes  with  constant  agitation,  there  is  produced  under 
these  conditions  alkali  cyanide  according  to  the  same  reaction 
as  above. 

As  in  the  case  in  the  dry  way,  only  one  half  of  the  alkali  is 
converted  into  cyanide.  The  reaction  may,  however,  be  com- 
pleted by  the  addition  of  finely  divided  charcoal,  which  reduces 
the  zinc  oxid  and  carbonates  to  an  equivalent  quantity  of  alkali. 
The  cyanide  solution  is  then  evaporated  to  dryness  in  suitable 
apparatus. 

We  do  not  know  what  results  have  been  produced  by  this  really 
peculiar  process.  One  may  truly  ask  oneself  if  the  reactions  do 
in  reality  take  place  as  the  authors  state,  and  if  the  charcoal  can 
really  reduce  zinc  oxid  under  the  conditions  mentioned.  These 
are  points  which  require  elucidation  in  order  that  this  original 
method  may  be  judged. 

The  disadvantages  inherent  to  the  use  of  the  oxids  or  carbonates 
of  the  alkalis  or  alkaline  earths  for  their  conversion  into  cyanides, 
and  to  which  we  called  attention  when  the  processes  utilizing  free 
atmospheric  nitrogen  were  studied,  reappear  in  the  ammonia  proc- 
esses using  these  same  oxids  or  carbonates.  The  most  serious  of 
all,  as  we  have  seen,  is  the  necessity  of  producing  the  high  tem- 
perature required  in  the  reduction  of  the  compound  used. 

As  in  the  processes  using  nitrogen,  it  was  sought  to  remedy 
this  by  making  use  of  the  alkali  metals  themselves. 

Hornig's  Process.  —  The  first  process  of  this  kind  is  that  of  Hornig 
(German  patent  No.  15467,  April  5,  1894;  Feb.  21,  1895).  This 


MANUFACTURE   OF  CYANIDES.  171 

process  deserves  to  be  mentioned  especially  on  account  of  its  original- 
ity. It  consists  in  making  the  vapors  (?)  of  the  alkalis  or  alkaline- 
earth  metals  (?)  (which  are  produced  in  a  separate  generator)  act 
upon  carbon  in  the  presence  of  nitrogen  or  ammonia,  or  upon  com- 
pounds of  nitrogen  and  carbon. 

The  process  is  united  directly  with  the  electrolytic  production 
of  the  alkali  metals.  When  the  vapors  of  these  metals  escape  from 
the  furnace  they  are  conducted,  by  means  of  a  current  of  water- 
vapor  (?),  into  an  inclosure  which  is  highly  heated  and  where  they 
€ome  in  contact  with  proper  amounts  of  carbon  and  nitrogen  neces- 
sary for  their  conversion  into  cyanide.  The  carbon  is  supplied  in 
the  form  of  carbonic  acid,  carbon  monoxid,  hydrocarbon,  or  even 
finely  divided  wood  charcoal;  the  nitrogen  is  supplied  in  the  form 
of  ammonia  or  of  atmospheric  nitrogen. 

The  cyanide  formed  immediately  flows  into  a  receiver — for  ex- 
ample, a  retort  communicating  with  the  lower  portion  of  the  ap- 
paratus, where  it  escapes  all  further  reaction. 

It  is  not  indispensable  that  the  alkali  metal  be  produced  elec- 
trolytically;  it  may  be  produced  by  any  other  apparatus  and  process 
known. 

When  nitrogen  is  used,  the  reaction  may  be  written 

Na  +  N+C=NaCN+C*_iHa;,   tyhuuu(s<ksM  tfc  ($, 
and  when  ammonia  and  carbon  monoxid  are  used  the  reaction  is 

Na  +  NH3 + CO  =  NaNH2  +  H  +  CO, 
NaNH2  +  H + CO  =  CNNa  +  H20 + H. 

The  technics  of  this  process  must  be  most  difficult,  especially 
in  that  which  relates  to  the  production  of  the  alkali  metal  vapors, 
and  it  is  difficult  to  explain  satisfactorily  how  these  vapors  are 
drawn  off  with  the  aid  of  steam.  We  doubt  therefore  if  this  process 
has  been  worked,  or  even  set  up  for  work,  on  an  industrial  scale. 
Nevertheless,  since  we  knew  of  its  originality  we  could  not  omit 
mentioning  it,  for  it  shows  all  the  more  how  far  the  researches  for 
the  synthetic  production  of  cyanides  has  been  carried. 

Schneider's  Process. — This  process  (German  patent  No.  9775,  June, 
1894;  Sept.,  1895)  has  already  been  much  improved.  It  makes 


172      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

use  of  alloys  of  alkali  metals  and  the  heavy  metals,  such  as  lead, 
zinc,  or  tin,  but  preferably  lead,  and  these  are  brought  into  reac- 
tion at  high  temperatures  with  nitrogenous  and  carbonized  mate- 
rials. 

The  advantages  in  using  this  method  are:  A  better  yield  due 
to  the  greater  specific  weight  of  these  alloys,  their  lesser  tendency 
to  oxidation,  and  their  greater  ease  of  handling  than  in  the  case 
of  the  free  alkali  metals.  The  author  recommends  using  an  inti- 
mate mixture  of  the  alloy  and  nitrogenous  and  carbonized  gases, 
stirring  with  a  stirrer,  or,  better  still,  by  injecting  the  gases  into 
the  melted  alloy. 

If  the  gas  be  brought  in  contact  with  the  surface  of  the  fusion 
only,  the  surface  of  the  alloy  soon  becomes  coated  with  a  layer  -of 
cyanide,  which  makes  any  further  conversion  into  cyanide  impossible. 

Here  is  how  the  author  would  proceed,  for  example,  to  produce 
sodium  cyanide : 

In  an  iron  crucible  80  cm.  high  and  35  cm.  in  diameter,  an  alloy 
of  lead  sodium  containing  10%  of  this  metal  is  melted  beneath 
a  layer  of  sodium  cyanide.  Into  this  bath,  heated  to  dull  redness, 
is  pumped  a  mixture  of  acetylene  and  ammonia  in  excess.  The 
cyanide  of  sodium  formed  collects  on  the  surface  of  the  alloy,  which 
grows  less  and  less,  finally  leaving  lead  almost  free  from  sodium. 

A  mixture  of  monomethylamine  and  ammonia  may  be  used. 

Castner's  Process. — The  process  which,  belonging  to  this  type, 
seems  the  simplest  and  at  the  same  time  the  most  economical,  and 
which  appears  to  give  the  best  results,  is  that  of  Hamilton  Young 
Castner. 

The  process  patented  by  Castner,  No.  239644,  June  28,  1894, 
is  but  a  repetition  of  patent  No.  239643  of  the  same  date,  which 
has  already  been  studied  in  a  previous  chapter,  but  with  this  differ- 
ence, that  the  author  substitutes  ammonia  for  nitrogen.  The  reaction 
may  therefore  be  expressed: 

NH3 + C + Na  =CNNa + H3. 

The  apparatus  is  the  same  as  that  used  in  the  case  of  nitrogen. 
As  the  author  states,  one  may  also  cause  dry  ammonia-gas  to  pass 
over  heated  charcoal,  and  the  resulting  gas,  consisting  of  ammo- 
nium cyanide,  CN-NH4,  then  passes  over  fused  sodium,  where  it 


MANUFACTURE   OF  CYANIDES.  173 

becomes  converted  into  sodium  cyanide,  with  ammonia  set  free, 
which  latter  may  be  recovered  and  used  again  in  the  conversion 
of  a  fresh  quantity  of  charcoal  into  ammonium  cyanide.  In  this 
way  the  reaction  is  continued  with  a  small  amount  of  ammonia. 
The  reactions  are: 


NH4  -CN  +  Na  =  CNNa  +  NH3  +  H. 

Castner  has  been  led  to  confirm  that  practically  in  both  these 
methods,  either  the  nitrogen  or  the  ammonia  process,  intermediary 
reactions  are  produced,  due  more  or  less  to  the  temperature  and 
to  the  proportion  of  constituents  present,  which  reactions  make 
the  manufacture  rather  difficult  unless  numerous  inconvenient  pre- 
cautions be  taken  to  avoid  loss  of  metal  or  of  nitrogen. 

These  observations  led  him  to  -  modify  his  process,  which  he 
did  in  the  French  patent  No.  242-938,  Nov.  17,  1894. 

In  this  new  process  the  operation  takes  place  in  two  successive 
stages,  so  that  the  yield  obtained  is  almost  theoretical,  according 
to  the  author,  and  the  general  character  of  the  method  is  simpli- 
fied. Moreover,  this  important  modification  allows  the  process  to 
be  carried  on  in  a  continuous  way. 

In  the  first  stage  of  his  process,  Castner  seeks  to  produce  an 
alkali  amide  by  passing  anhydrous  ammonia-gas  over  sodium  heated 
at  a  temperature  of  300-400°,  according  to  the  reaction 


In  the  second  stage  he  converts  this  amide  into  cyanide  by 
bringing  it  in  a  melted  state  in  contact  with  charcoal: 

-NaNH2+C  =  CNNa  +  H2. 

In  practice  the  process  is  carried  on  by  means  of  two  retorts. 
In  the  first  retort,  specially  constructed,  the  description  of  which 
will  follow,  the  conversion  of  the  alkali  metal  into  amide  takes  place, 
and  in  the  second,  which  is  somewhat  similar  to  that  used  by  Castner 
in  his  first  process,  the  second  phase  of  the  process  takes  place,  i.e., 
the  conversion  of  the  amide  into  cyanide. 

One  half  of  the  rectangular  retort  B  (Figs.  9,  10,  11)  is  provided 
with  partitions  C,  which  reach  low  enough  to  plunge  into  fused 


174       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

metal  D.    The  ends  of  these  partitions  are  cut  short  in  order  to 
allow  the  gas  or  vapors  to  follow  the  direction  indicated  by  the 


FIG.  9. — Castner's  Process.      Furnace  (A)  with  Rectangular  Retort  (B}  (Elevation). 

arrows.     The  upper  half  of  the  retort  is  provided  with  a  forked 
entrance  tube  L,  an  exit  tube  M,  a  bent  tube  with  hopper  N  pro- 


^3 

r 

\ 

I 

? 

% 

s^ 

^ 

c: 

E 

c 

c 

H 

F 

ccr 

V, 

S 

v+ 

S 

V 

s 

FIG.  10. — Castner's  Process.     Perspective  of  Half  of  the  Retort. 

vided  with  a  valve  0.  The  lower  half  is  lined  with  partitions  E  and 
F,  the  former  reaching  a  little  above  the  level  of  the  latter,  and 
with  the  partition  H  reaching  a  little  below  partition  F.  It  con- 
tains several  openings  shown  in  K. 

The  bottom  of  the  retort  is  provided  with  an  exit  tube  P,  and 
another  one  R.  The  rectangular  retort  is  composed  of  iron. 

The  following  is  the  method  of  procedure  in  practice:  The  retort 
B  is  heated  to  390-400°,  then  dry  ammonia-gas  is  conducted  into 
it,  through  the  tubes  L  and  U ,  in  order  solely  to  expel  the  air. 
When  this  is  done,  the  sodium,  which  is  melted  in  N,  is  allowed 


MANUFACTURE  OF  CYANIDES.  175 

to  flow  up  to  the  level  of  the  dotted  line  between  E  and  H.  The 
flow  of  the  metal  is  then  for  the  time  being  stopped. 

The  intake  of  ammonia  is  regulated  according  to  the  capacity 
of  the  retort;  the  sodium  flows  only  at  regular  intervals,  that  is, 
for  every  17  kg.  of  ammonia,  23  kg.  of  sodium  are  required. 

The  amide  which  forms  at  the  surface  of  the  bath  melts  and 
sinks  to  the  lower  part.  It  fills  the  space  included  between  H  and  F, 
driving  the  sodium  out  through  the  tube  R.  The  overflow  of  amide 
thus  becomes  regulated  and  may  be  collected  in  closed  vessels, 
being  afterward  subjected  to  the  further  treatment  in  the  process 


FIG.  11. — Cross-section  of  the  Retort. 

of  forming  cyanide,  or  else  it  may  be  transferred  directly  by  appro- 
priate appliances  to  the  retort  shown  in  Fig.  12,  where  the  second 
phase  of  the  process  takes  place.  This  second  retort  is  filled  with 
wood  charcoal  and  heated  to  dull  redness;  the  amide  flows  through 
the  tube  S,  and  the  hydrogen  formed  escapes  through  the  tube  W, 
while  the  cyanide  produced  flows  in  X.  From  time  to  time  fresh 
charcoal  is  added  in  order  to  replace  that  which  has  been  used. 

Castner  is  one  of  the  few  manufacturers  who  faced  the  problem 
of  the  synthetic  production  of  cyanide  at  a  favorable  moment.  His 
discoveries  certainly  mark  one  of  the  most  important  advances  in 
the  history  of  this  interesting  industry.  His  process  has  been  taken 
up  in  Germany.  Important  improvements  have  been  added,  and 
the  day  is  perhaps  not  far  distant  when  a  real  synthetic  process 
for  the  production  of  cyanide  along  this  line  will  appear. 

Process  of  the  Deutsche  Gold  und  Silber  Scheide  Anstalt. — Thus 
it  is  that  the  above  important  German  firm  has  just  recently  taken 
out  two  patents,  one  for  the  preparation  of  cyanamide,  the  other 
for  the  preparation  of  alkali  cyanides,  both  of  which  are  based  on 
the  formation  of  alkali  amides,  and  according  to  information 
we  have  been  able  to  gather  have  given,  up  to  the  present  time, 


176      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

satisfactory  results.  These  two  patents  present  a  lively  interest, 
and  the  reader  will  take  it  kindly  of  us  if  we  reproduce  them  here 
almost  entirely. 

The  first  of  these  patents  (No.  308170)  concerns  the  preparation 
of  cyanamide.  Up  to  this  time  this  body  had  been  considered  diffi- 
cult of  preparation.  Frank  and  Caro,  in  a  process  of  cyanide  manu- 
facture which  we  have  previously  described,  had  already  made 


FIG.  12. — Castner's  Process.     Second  Phase  of  the  Process. 

known  a  more  practical  means  of  preparing  it  on  an  industrial  scale. 
The  Deutsche  Gold  und  Silber  Scheide  Anstalt  has  since  that  time 
been  led  to  find  a  process,  simple  as  well  as  practical,  which  allows 
its  preparation  in  a  really  economical  way. 

The  formula  of  cyanamide  is  H2N-CN.  With  metals  it  yields 
metallic  compounds  which  may  correspond  to  the  formula  M  or 
M2-CN-N.  Thus,  with  sodium  it  yields  monosodium  cyanamide, 
Na-N-CN,  and  disodium  cyanamide,  Na2-N-CN. 


MANUFACTURE  OF  CYANIDES.  177 

The  dialkali  cyanamide  is  prepared  by  the  Deutsche  Gold  und 
Silber  Scheide  Anstalt,  by  starting  with  the  alkali  amide  obtained, 
as  is  well  known,  by  the  action  of  ammonia  on  an  alkali  metal  at 
a  temperature  higher  than  the  melting-point,  but  lower  than  the" 
point  of  the  dissociation  of  the  amide  and  the  ammonia-gas. 

The  process  is  based  on  this  still  unknown  fact  that  carbon  at 
about  400°  displaces  hydrogen  of  the  amide  and  yields  cyanamide, 
while  at  a  higher  temperature,  about  800°,  it  yields,  as  is  known, 
cyanides. 

If  therefore  carbon  either  in  the  solid  state  or  in  the  form  of 
hydrocarbon  gas  be  brought  in  contact,  at  a  temperature  of  about 
400°,  with  an  alkali  amide  prepared  according  to  well-known  methods, 
and  in  the  melted  state,  cyanamide  will  be  formed.  Solid  or  melted 
amide  may  also  be  brought  in  contact  with  a  solid  bath  composed 
of  a  body  rich  in  carbon  and  heated  to  a  suitable  temperature,  or 
likewise  ammonia  at  a  temperature  of  400°  may  be  conducted  into 
a  mixture  of  melted  alkali  metal  and  charcoal;  but  in  either  case, 
the  temperature  must  be  successively  increased  with  the  corre- 
sponding formation  of  cyanamide  until  this  temperature  be  some- 
what higher  than  the  point  of  fusion  of  the  cyanamide. 

Such  is  the  process  for  the  preparation  of  the  dialkali  cyanamide 
as  brought  out  by  the  Deutsche  Gold  und  Silber  Scheide  Anstalt.  It 
has  resulted  in  obtaining  in  a  practical  way  the  synthseis  of  cya- 
nides, as  we  shall  presently  see.  In  fact,  when  treated  with  charcoal 
at  a  high  temperature  the  cyanamide  becomes  converted  into  cya- 
nide. This  method  of  the  preparation  of  cyanides  is  an  improvement 
over  that  of  Castner,  described  above,  in  that  the  alkali  amide  used 
by  Castner  decomposes  at  a  low  temperature — above  400° — while 
cyanamide  withstands  a  temperature  up  to  800°. 

In  practice  the  Deutsche  Gold  und  Silber  process  is  carried  out  as 
follows : 

In  a  crucible  mounted  and  built  in  a  furnace  which  may  be  well 
and  easily  regulated,  sodium  is  melted  with  charcoal  or  carbona- 
ceous compound  (hydrocarbon  or  other  compound)  in  such  quantity 
as  will  suffice  to  convert  all  of  the  metal  into  cyanide.  When  the 
metal  has  been  melted,  ammonia  is  then  conducted  at  a  temperature 
somewhat  raised  (400-600°).  Under  these  conditions  alkali  amide 
is  formed  which,  under  the  action  of  a  portion  of  the  charcoal,  becomes, 


178       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS 

in  its  turn,  converted  into  cyanamide  dialkaline,  Na2-N-CN.  By 
raising  the  temperature  to  700-800°  this  cyanamide  in  contact  with 
the  remainder  of  the  charcoal  forms  the  final  product,  sodium 
cyanide,  NaCN. 

But  as  the  cyanide  (a  body  containing  carbon)  may  also  be  used 
in  the  formation  of  cyanamide,  the  process  may  be  so  arranged  that 
a  portion  of  the  alkali  cyanide  found  in  the  crucible  at  the  end  of 
the  operation  may  be  always  left  therein  in  sufficient  quantity  to 
produce  the  cyanamide  of  the  next  operation,  and  only  sufficient 
charcoal  to  convert  this  cyanamide  into  cyanide  need  be  added.  In 
any  case  a  quantity  of  alkali  cyanide  corresponding  to  the  alkali 
metal  and  the  ammonia  used  is  always  obtained. 

As  may  easily  be  seen,  this  process,  which  is  very  ingenious,  is 
both  practical  and  economical.  Over  all  the  methods  thus  far 
invented,  it  has  the  following  advantages,  which  are  to  be  attentively 
considered : 

1.  The  operation  is  carried  on  at  quite  low  temperatures,  which 
prevents,  to  a  considerable  extent,  loss  either  of  alkali  or  of  cyanide, 
as  well  as  any  deterioration  of  the  apparatus. 

2.  The  process  requires  only  a  restricted  as  well  as  simple  appara- 
tus, since  the  whole  operation  may  be  carried  out  in  one  and  the 
same  crucible. 

3.  The  yield  is  quite  high,  and,  according  to  the  authors,  is  very 
near  the  theoretical. 

These  advantages  are  certainly  to  be  considered,  and  there  is  no 
doubt  but  that  the  process  of  the  Deutsche  Gold  und  Silber  Scheide 
Anstalt  will  be  applied  on  a  really  important  scale,  thus  allowing  the 
cyanide  to  be  delivered  at  a  remunerative  price. 

We  have  already  called  attention  to  the  fact  that  many  investi- 
gators had  explained  the  formation  of  cyanides,  resulting  from  the 
action  of  ammonia  and  carbon  monoxid,  through  the  intermediary  of 
formamide.  We  have  also  seen  that  the  accepted  theory  is  rather 
that  of  the  formation  of  potassamide.  Yet  several  processes  are 
based  on  the  former  hypothesis. 

Lambilly's  Process. — Lambilly,  whose  name  appears  at  the  head 
of  most  of  the  innovations  of  the  cyanide  industry,  is  one  of  the  first 
to  have  based  a  process  for  the  manufacture  of  cyanide  on  this  class 
of  reaction. 


MANUFACTURE  OF  CYANIDES.  179 

In  his  French  patent  (No.  232697,  1893)  Lambilly  carried  on  his 
new  method  as  follows: 

Into  one  or  several  tubes  heated  to  a  temperature  between  40° 
and  150°  and  filled  with  porous  substances,  a  mixture  of  carbon 
monoxid  and  ammonia  is  conducted,  according  to  the  reaction 

NH3+CO  =  H.CO-NH2. 

formamide 

This  formamide,  when  heated  at  a  temperature  above  210°  in  a 
second  group  of  tubes  filled,  as  in  first  case,  with  porous  substances, 
is  decomposed  with  formation  of  hydrocyanic  acid: 


.    ^( 


__ 

Martin's  Process.  —  This  process  (French  patent  No.  262949,  Jan. 
11,  1897)  consists  in  bringing  atmospheric  nitrogen  into  reaction  with 
methane  in  definite  quantities  (the  amounts  are  not  indicated  by 
the  author)  contained  in  a  retort  constructed  of  refractory  brick 
which  is  charged  with  porous  substances  which  have  previously 
been  metallized  with  platinum,  titanium,  vanadium,  or  magnesium. 
Under  these  conditions  the  methane  breaks  up  into  acetylene  and 
hydrogen. 

Under  the  influence  of  heat,  nitrogen,  and  hydrogen,  the  acetylene 
in  the  nascent  state  is  decomposed  into  gaseous  cyanogen  products, 
which  are  conducted  into  a  cylinder  adjoining  the  retort  and  con- 
taining fragments  of  potassa-lime  heated  to  redness.  In  this  way 
potassium  cyanide  is  obtained,  which  may  be  separated  by  filtration 
and  crystallization.  We  are  not  in  possession  of  any  further  data 
concerning  this  process,  nor  of  its  working. 

Clock's  Process.  —  This  process  (German  patent  No.  108152,  March 
15,  1899)  still  utilizes  the  property  which  formamide  has  of  breaking 
up  into  water  and  hydrocyanic  acid. 

Clock  heats,  in  an  autoclave  at  200-300°,  ammonium  formate 
alone,  or  mixed  with  ammoniacal  zinc  chloride,  yielding  formamide 
which  distils 

HC02NH4  =  H20  +  H  .  CO  -  NH2, 

its  vapors  being  conducted  over  melted  potassa  or  soda,  or  a  mixture 
of  the  two,  heated  to  250-350°.    If  the  formamide  still  contains 


180      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

moisture  and  unconverted  ammonium  formate,  the  alkali  should  be 
heated  above  360°.  The  reaction  consists  in  dehydrating  the  forma- 
mide  under  the  influence  of  the  melted  alkali,  a  dehydration  which 
gives  rise  to  hydrocyanic  acid  which  becomes  fixed  immediately  by 
the  alkali  with  formation  of  cyanide. 

Two  other  processes  which  are  quite  peculiar  and  original  and 
which  are  based  on  quite  different  principles  from  those  already 
studied  will  be  mentioned. 

Huntington's  Process. — The  first  is  that  of  Kirby  Huntington 
(English  patent  No.  14855,  Aug.  6,  1895;  German  patent,  No.  16931, 
Jan.  1896,  April,  1897;  French  patent  No.  253740,  Feb.  5,  1896). 

In  this  method  the  inventor  produces  hydrocyanic  acid  by  means 
of  rapid  deflagration  of  a  mixture  of  equal  volumes,  or  of  105  vols. 
nitric  oxid  and  100  vols.  acetylene  in  a  cylinder  with  firm  walls: 

C2H2 + NO  =  CNH + CO  +  H. 

The  mixture  of  the  two  gases  serves  as  a  motive  force  for  an 
ordinary  gas-motor  by  the  use  of  the  electric  spark. 

The  gases  which  issue  from  the  cylinder  pass  through  a  series  of 
absorption  apparatus  filled  with  strong  alkali  solutions.  The  hydro- 
cyanic acid  is  absorbed  and  forms  cyanides,  whereas  the  hydrogen 
and  the  carbon  monoxid  are  collected  in  a  gasometer  and  may  be 
used  as  fuel. 

This  process  does  not  appear  to  us  to  have  given  satisfactory 
enough  results  to  warrant  its  use  industrially. 

Hoyermann's  Process. — The  second  of  these  processes  is  that  of 
Hoyermann  (French  patent  No.  294979,  Dec.  5,  1899).  It  is  but  a 
modification  of  Huntington's  process,  in  which  it  is  sought  to  avoid 
the  formation  of  carbon  monoxid  and  hydrogen  which  takes  place 
in  that  process.  Instead  of  using  nitric  oxid,  Hoyermann  employs 
nitrogen,  according  to  the  reaction  already  indicated  by  Berthelot, 

C2H2+2N=2CNH. 

The  reaction  takes  place  in  a  carbide  electric  furnace.  The 
electrodes  are  hollow  and  are  used  for  the  introduction  of  the  acety- 
lene and  the  nitrogen  which  they  bring  separately  into  the  zone  of 
action  of  the  luminous  arc.  The  mixture  and  the  union  of  the  two 


MANUFACTURE  OF  CYANIDES.  181 

gases  take  place  at  that  point.  Calcium  carbide  may  likewise  be 
produced  in  the  furnace,  and  on  the  addition  of  water-vapor,  acetylene 
may  be  formed.  At  the  same  time,  the  introduction  of  air,  which 
comes  into  contact  with  the  acetylene,  yields  hydrocyanic  acid  under 
the  action  of  the  electric  arc.  The  hydrocyanic  acid  thus  formed  is 
removed  by  means  of  a  suction-pump,  collected  and  absorbed  by 
suitable  means. 

Moreover,  the  process  may  be  made  continuous.  In  fact,  under 
the  action  of  water-vapor,  calcium  carbide  becomes  decomposed 
into  acetylene  and  lime,  which  latter,  on  careful  addition  of  pieces 
of  charcoal,  may  be  intermittently  transformed  anew  into  carbide. 

This  process  does  not  seem  to  us  to  be  any  better  suited  to  indus- 
trial purposes  than  the  preceding  one. 

Nitric  and  nitrous  nitrogen  have  also  been  employed. 

Roussin's  Process. — Roussin  has  noted  that  if  a  mixture  of 
fused  potassium  acetate,  potassium  nitrate,  and  potassium  carbo- 
nate be  dissolved  in  a  small  amount  of  water  .and  evaporated  to  dry- 
ness  and  the  residue  be  fused,  it  deflagrates  violently  at  350°,  leav- 
ing behind  a  black  spongy  mass  containing  a  large  quantity  of 
cyanide  of  potassium  mixed  with  potassium  carbonate  and  char- 
coal. But  this  method  has  one  disadvantage  in  that  3/4  of  the 
carbon  of  the  acetate  is  converted  into  carbonic  acid  by  the  oxygen 
of  the  nitrate.  To  overcome  this  disadvantage  Roussin  proposes 
the  use  of  potassium  nitrite  mixed  with  lampblack,  acetate,  and 
carbonate  of  potash. 

Kerp's  Process.— Wilhelm  Kerp  (Ber.  d.  d.  Chem.  Gesell.  1897, 
p.  610)  observed  that  when  sodium  acetate  is  fused  with  potassium 
nitrite,  there  is  formed  potassium  cyanide  according  to  the  reaction 

CH3  •  CO  •  ONa + KN02  =  C03HNa  +  CNK + H20. 

The  yield  of  cyanide  depends  to  a  large  extent  on  the  tempera- 
ture; in  no  case  does  it  exceed  25%,  and  the  reaction  often  yields 
considerable  quantities  of  hydrocyanic  acid.  According  to  the 
inventor,  the  reaction  should  take  place  thus:  In  the  first  phase 
of  the  reaction  there  is  formed  caustic  soda  and  nitroacetate  of 
sodium: 

NaOH+NO-CH2-CO-ONa. 


182       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

This  salt  is  then  broken  up  into  bicarbonate  of  soda  and 
hydrocyanic  acid: 

NO  -CH2  -CO  -ONa= C03NaH+CNH. 

A  portion  of  the  hydrocyanic  acid  thus  formed  combines  with 
the  caustic  soda,  the  rest  escaping.  This  is  therefore  a  process 
which  is  not  applicable  to  industrial  purposes. 

Kellner's  Process.— This  process  (French  patent  No.  252282,  Dec. 
9,  1895)  consists  in  subjecting  to  the  electric  arc  an  alkali  nitrite  or 
nitrate  with  or  without  addition  of  charcoal  to  facilitate  the 
reaction. 

Siepermann  had  previously  tried  to  utilize  the  same  reaction, 
but  in  a  reverberatory  furnace.  With  this  object  in  view,  he  injected 
pulverized  alkali  nitrite  or  nitrate  into  a  reverberatory  furnace  by 
means  of  compressed  air,  the  furnace  being  charged  with  charcoal 
alone  or  charcoal  to  which  had  been  added  a  small  amount  of  car- 
bonate. The  cyanide  formed  flowed  through  a  draft-hole  situated 
in  the  most  sloping  place  of  the  sole.  As  a  portion  of  the  cyanide 
formed  became  volatilized  at  the  high  temperature  at  which  it  was 
necessary  to  carry  on  the  reaction,  the  gases  escaping  the  furnace 
passed  through  condensation  chambers  or  absorption  towers,  where 
they  gave  up  this  salt. 

Grossmann's  Process. — Jacob  Grossmann's  process  (1900)  is  a 
rather  curious  one.  It  is  based  on  the  reaction,  already  known, 
that  if  liver  of  sulphur  be  melted  in  the  presence  of  charcoal,  and 
then  ammonium  sulphate  be  added  to  the  fused  mass,  a  very  lively 
reaction  (sometimes  even  an  explosion)  takes  place  which  yields 
sulphocyanide  of  potassium.  This  process,  studied  by  Fleck  in 
1863,  had  not  been  tried  on  an  industrial  scale.  Grossmann  took 
up  the  process  anew,  and  modifying  the  nature  of  the  reactions, 
made  out  of  it  a  method  for  the  direct  manufacture  of  cyanides. 
He  noted  that  if  ammonia  be  passed  over  a  mixture  of  liver  of  sul- 
phur and  charcoal  heated  to  redness  (700-800°),  potassium  cyanide 
is  formed;  sulphocyanide  is  formed  only  in  a  secondary  way,  the 
greater  portion  of  the  sulphur  being  converted  into  either  hydrogen  • 
sulphide  or  ammonium  sulphide. 

If  the  sulphide  already  formed  be  used,  the  process  requires 


MANUFACTURE  OF  CYANIDES.  183 

equal  parts  of  sulphide  and  of  wood  charcoal;  when  liver  of  sul- 
phur is  used  the  following  proportions  are  necessary: 

Carbonate  of  potash  (pure) 100  parts 

Charcoal 120-140    " 

Sulphur 24    " 

These  quantities  are  necessary  to  prevent  heaping  together. 
III.  SPECIAL  PROCESSES. 

Under  this  heading  will  be  mentioned  processes  which  have 
been  proposed  for  the  production  of  cyanides,  and  which  do  not 
belong  to  any  of  the  preceding  classes  According  to  information 
obtained  by  us,  it  follows  that,  with  the  exception  of  Dr.  Bueb's 
process,  the  other  processes  have  either  not  been  tried  at  all  or  to 
a  very  limited  degree ;  yet  we  shall  mention  them  in  order  to  show 
the  variety  of  ideas  brought  out  concerning  the  manufacture  of 
cyanides,  all  of  which  indicate  the  interest  and  importance  of  this 
question. 

Process  of  the  Chemische  Fabrik  Aktiengesellschaft. — One  of  the 
most  interesting  processes  of  this  class  is  that  of  the  Chemische 
Fabrik  Aktiengesellschaft  of  Hamburg  (German  patent  No.  5242, 
1894-1895,  and  French  patent  No.  241146,  1894-1895). 

It  consists  in  heating  to  redness  sodium  or  potassium  carbazol 
with  or  without  the  addition  of  sodium  or  potassium  hydrate  or 
carbonate,  and  in  case  it  is  desired  to  produce  ferrocyanides,  with 
the  addition  of  iron. 

Carbazol  is  obtained  in  the  residues  from  the  purification  of 
crude  anthracene  (by  means  of  benzene,  sulphurous  acid,  etc.), 
which  residues  contain  large  amounts  of  it.  These  residues  are 
treated  with  dry  or  slightly  moist  caustic  alkali  corresponding  to 
the  amount  of  carbazol  present.  This  treatment  takes  place  in  a 
cast-iron  pot  provided  with  a  stirrer.  Heat  is  applied  gradually 
till  the  temperature  reaches  260-280°  when  potassa  is  used,  and 
to  320-340°  with  soda.  This  temperature  is  maintained  for  several 
hours.  The  alkali  carbazol  formed  separates  out  clearly  from  the 
other  compounds  'hydrocarbons,  etc.).  It  is  collected  separately 
and  to  it  is  added  an  excess  of  caustic  soda  or  potash  or  their  car- 
bonates, and  i  on,  if  the  object  be  to  prepare  ferrocyanides.  The 
mixture  is  then  heated  to  bright  redness.  The  fused  mass  is  taken 


184   METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

up  with  water  and  treated  according  to  any  of  the  ordinary  methods 
for  the  separation  of  cyanide  or  ferrocyanide. 

In  practice  the  method  of  procedure  is  as  follows:  200  kilos  of 
residue  from  the  purification  of  anthracene,  containing  40%  or 
thereabouts  of  carbazol,  are  treated  with  30  kilos  caustic  potash. 
The  heat  is  kept  at  260-280°  until  all  the  water  separated  by  the 
union  of  the  carbazol  with  the  potassa  has  distilled,  which  requires 
about  three  hours.  The  stirrer  is  then  stopped,  and  after  a  quarter 
of  an  hour's  repose,  the  product  is  run  into  moulds.  The  whole 
solidifies;  but  after  cooling,  it  is  easy  to  separate  the  solid  cake 
of  potassium  carbazol  which  lies  at  the  bottom  of  the  moulds  from 
the  more  or  less  soft  crystalline  magma  formed  with  floating  anthra- 
cene carbides.  The  crude  potassium  carbazol  is  crushed  and  again 
heated  in  an  apparatus  similar  to  the  one  mentioned  above,  capa- 
ble of  being  heated  to  bright  redness.  The  temperature  is  gradu- 
ally raised  to  this  point,  and  under  these  conditions  the  potassium 
carbazol  becomes  converted  into  cyanide  with  separation  of  car- 
bon and  liberation  of  some  ammonia  and  combustible  gases.  A 
greater  yield  may  be  obtained  by  carrying  on  the  fusion  in  the  pres- 
ence of  an  alkali  used  as  a  flux.  Unfortunately  we  have  no  data 
concerning  the  yield  produced  by  this  process. 

VidaPs  Process.— This  process  (German  patent  No.  2868,  1897; 
French  patent  No.  274875,  Feb.  9,  1895)  uses  phospham. 

If  a  mixture  of  6  kilos  of  phospham  and  19  kilos  potassium  car- 
bonate be  heated  to  redness  up  to  complete  desiccation  of  the  phos- 
phorus, there  will  be  formed  potassium  cyanate  and  phosphate 
according  to  the  reaction 

PN2H + 2C03K2  =  PO,K2H + 2CNOK. 

The  mass  may  be  treated  with  water  or  alcohol,  which  dissolves 
the  cyanate,  leaving  the  less  soluble  phosphate  behind. 

But  if  to  the  charge  used  above  charcoal  be  added  in  the  fol- 
lowing amounts, 

Phospham 6  kilos 

Potassium  carbonate.. 19     " 

Charcoal 1J  ". 


MANUFACTURE  OF  CYANIDES.  185 

cyanide  of  potassium  will  be  obtained: 

PN2H + 2C03K2 + 2C  =  2CNK + 2CO + P04K2H. 

By  adding  0.8  kilo  of  iron  or  4  kilos  of  sulphur  to  the  above 
charge  ferrocyanide  or  sulphocyanide  will  be  obtained. 

The  carbonate  may  be  replaced  by  neutral  or  acid  oxalate  which 
yields  cyanogen  or  hydrocyanic  acid,  which  escapes,  or  the  phospham 
may  be  heated  to  150-200°  with  fatty  acids.  Thus,  with  formic, 
acid,  there  is  formed  hydrocyanic  acid: 

PN2H+2C02H2=P04H3 +2CNH. 

The  operation  is  carried  on  as  follows :  60  kilos  phospham  are  placed 
in  an  enamelled  cast-iron  pot  and  heated  in  an  oil-bath  to  150-200°. 
Then  48  kilos  formic  acid  or  63  kilos  acetic  acid  are  rapidly  run  in. 
Hydrocyanic  acid  is  collected  by  the  usual  means. 

We  do  not  know  whether  this  process  has  been  tried. 

To  conclude  this  last  part,  we  shall  take  up  certain  processes 
whose  object  is  to  extract  in  the  form  of  cyanide  the  nitrogen  con- 
tained in  the  residues  of  the  refinery  and  of  the  distillery.  The 
molasses  and  vinasse  contain,  as  is  well  known,  variable  amounts 
of  nitrogen  (0.5-2.5%).  Various  methods  have  been  proposed  for 
regaining  this  nitrogen  in  the  form  of  ammoniacal  liquors  or  of 
ammonium  sulphate,  but  most  of  these  methods  have  not  continued 
in  use  for  any  length  of  time.  The  product  obtained  is  largely 
contaminated  with  amines  formed  during  ignition,  which  are  diffi- 
cult to  separate  from  the  ammonia.  Among  them  are  trimethyl- 
amine  dimethylamine,  monomethylamine,  monobutylamine,  and 
monopropylamine.  Moreover,  the  gases  which  escape  during  the  dis- 
tillation of  the  molasses  and  vinasses  spread  abroad  in  the  surround- 
ing atmosphere  an  odor  which  is  tainted  and  injurious  to  the  public 
health.  Besides  avoiding  this  disagreeable  odor,  Bueb's  processes 
furnish  cyanide  cheaply  and  in  a  relatively  simple  manner. 

Bueb's  Processes.— In  his  first  French  patent  (No.  246282,  April 
1,  1895)  Dr.  Julius  Bueb  conducts*  the  gases  which  escape  during  the 
distillation  of  the  vinasses  and  molasses  into  a  system  of  vessels 
or  refractory  tubes  heated  to  bright  redness  or  to  a  white 
heat. 


186       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

In  this  way  all  the  volatile  compounds  of  nitrogen  which  they 
contain  are  entirely  converted  into  ammonium  cyanide  mixed  with 
a,  little  ammonium  carbonate.  On  emerging  from  the  system  of 
tubes,  the  gases  pass  into  suitable  solutions  (ferric  salts). 

The  vinasses  at  40°  B.  are  introduced  into  the  furnace  A  (Figs. 
13,  14,  15,  16).  Toward  this  end  they  are  made  to  flow  from  the 
upper  reservoir  a  into  the  receptacle  &,  and  by  means  of  a  siphon 
c  into  the  retort,  where  a  liberation  of  gas  immediately  begins.  The 
gases  of  the  distillation  are  collected  in  the  tube  e  and  transmitted 


FIG.  13. — Bueb's  Process. 


directly  into  the  pipes  /.  These  pipes  go  through  the  furnace  in 
zigzags,  and  are  so  arranged  that  the  gases  require  about  15  seconds 
in  passing  through. 

After  passing  through  these  pipes,  the  gases  are  conducted  to 
the  absorption  apparatus.  The  heating  of  the  furnace  may  be  done 
by  means  of  the  gases  from  the  distillation  after  first  freezing  them 
from  the  cyanogen  compounds.  They  first  heat  the  pipes  /  by 
passing  under  them  by  way  of  the  passage  k;  then  above,  through 
the  space  ki ; .  and  lastly  they  likewise  heat  the  retort  by  way  of  the 
passage  k2.  The  temperature  of  the  pipes  is  between  1000  and 
1100°,  that  of  the  retorts  700-800°. 


MANUFACTURE   OF  CYANIDES. 


187 


By  means  of  this  process,  Bueb  obtains  a  gaseous  mixture  com- 
posed to  a  large  extent  of  hydrocyanic  and  carbonic  acids.  In 
order  to  separate  these  two  gases,  he  uses  the  same  method  that 


FIG.  14. — Bueb's  Apparatus. 

is  used  in  extracting  cyanogen  from  coal-gas ;  that  is,  its  absorption 
by  means  of  iron  salts,  the  result  of  which  being  the  formation  of 


FIG.  15. — Bueb's  Apparatus. 

a  double  ferrocyanide  which  may  then  be  converted  at  will  into 
alkali  cyanide. 

Later,  Bueb  was  led  to  separate    hydrocyanic  acid  from  car- 


188        METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 


MANUFACTURE  OF  CYANIDES. 

bonic  acid  directly  in  the  form  of  alkali  cyanide.  To  this  end  he 
proceeds  as  follows  (French  patent  No.  283968,  Dec.  13,  1898). 

The  gaseous  mixture  is  first  cooled  down,  and  in  case  it  con- 
tains ammonia,  it  is  made  to  pass  into  dilute  sulphuric  acid  (20%). 

Thence  it  is  conducted  to  a  tower  through  which  a  stream  of 
very  strong  alcohol  flows  in  the  opposite  direction.  The  alcohol 
dissolves  only  the  hydrocyanic  acid,  so  that  a  solution  of  hydro- 
cyanic acid  flows  at  the  bottom  of  the  tower.  This  solution  is 
subjected  to  a  fractional  distillation,  and  the  vapors  of  hydrocyanic 
acid  are  then  combined  in  the  usual  way. 

For  this  purpose  it  is  possible,  and  it  is  moreover  the  method 
which  the  author  particularly  recommends,  to  have  the  vapors  of 
acohol  and  hydrocyanic  acid  pass  through  an  alcoholic  caustic 
alkali  solution.  Alkali  cyanide,  which  is  formed,  being  quite  diffi- 
cultly soluble  in  alcohol,  is  precipitated  in  the  form  of  a  white  powder. 
The  alcohol  is  condensed  and  used  again  in  repeating  the  operation. 

After  absorption,  the  vessels  containing  the  lye,  when  cooled, 
are  connected  with  an  aspirator.  After  the  aspiration,  there  remains 
in  the  apparatus  practically  pure  alkali  cyanide  (98%).  The  mother 
liquors  which  flow  from  the  aspirator,  and  which  contain  2  to  4% 
alkali  cyanide,  are  conducted  into  a  saturation  apparatus  placed 
in  front  of  the  tower  through  which  alcohol  flows,  and  the  gases 
passing  through  precipitate  the  alkali  as  carbonate,  while  the  alcohol 
becomes  saturated  with  the  hydrocyanic  acid  which  is  converted 
into  cyanide  as  before. 

In  his  patent  No.  296793,  taken  out  in  1900,  Bueb  states  that 
during  the  dry  distillation  of  vinasses  the  gases  which  pass  through 
the  narrow  tubes  where  the  conversion  into  cyanide  takes  place 
deposit,  when  heated,  particles  of  carbon  which  obstruct  these 
pipes  and  hinder,  to  a  considerable  extent,  the  regulation  of  heat. 
In  order  to  remedy  this  inconvenience,  he  proposes  the  following 
arrangement : 

The  distillation  takes  place  in  retorts  filled  with  pieces  of  refrac- 
tory substances  previously  heated  to  the  required  temperature. 
When  this  temperature  has  been  reached,  the  heating  is  discon- 
tinued, and  the  gases  are  passed  through.  These  gases  become 
rapidly  heated  through  the  heat  of  these  refractory  contact-bodies 
and  are  converted  into  cyanide  compounds.  During  this  opera-* 


190      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

tion,  the  gases  deposit  upon  these  contact-bodies  charcoal  to  such 
an  extent  that  they  become  coated  therewith.  When  this  point 
has  been  reached,  the  supply  of  gases  to  this  oven  is  stopped,  and 
instead  they  are  conducted  to  another  oven  already  heated  during 
this  first  stage  of  the  process.  During  the  second  stage  the  appa- 
ratus, which  has  been  exhausted,  is  heated  anew,  and  at  the  same 
time  the  calorific  power  of  the  deposited  carbon  is  utilized  in  heat- 
ing the  refractory  contact-bodies  for  the  next  operation.  Thus,  the 
process  may  be  carried  on  continuously,  and  besides,  the  deposited 
charcoal,  which  used  to  be  a  serious  danger  in  the  cyaniding  process, 
is  utilized. 

Bueb's  processes  are  used  on  an  industrial  scale  to  a  consider- 
able extent  in  Germany,  where  quite  favorable  results  are  obtained 
they  are  regularly  in  operation  in  one  of  the  largest  sugar- works. 
The  raw  salts  of  vinasses  obtained  appear  to  be  better.  In  any  case, 
the  process  may  be  easily  adapted  to  refineries  and  distilleries  with- 
out modifying  in  the  least  their  usual  course,  and  it  would  allow 
considerable  extra  revenue  to  be  derived  from  the  beet  residues. 

The  idea  is,  moreover,  not  entirely  new,  for  from  1894  the  Societe 
anonyme  de  Croix  (Nord)  manufactured  cyanides  from  trimethyl- 
amine. As  is  known,  this  compound,  corresponding  to  the  formula 
N(CH3)3,  is  obtained  in  large  quantities  in  the  dry  distillation  of 
beet  residues.  It  is  formed  by  the  decomposition  of  the  two  alka- 
loids found  in  beet-juice,  betaine  and  cholin.  The  ordinary  molasses 
may  contain  as  much  as  5-13%  betaine.  From  Bressler's  investi- 
gations, it  follows  that  in  100  parts  of  nitrogen  of  beet  residues, 
20.67  parts  belong  to  betaine  and  20.32  to  cholin;  and  in  100  parts 
nitrogen  in  the  products  of  distillation  of  the  beet  residues,  26.76 
parts  are  in  the  form  of  trimethylamine.  Moreover,  most  of  the 
alkaloids,  on  decomposing,  yield  trimethylamine,  and  the  distilla- 
tion of  wood  also  gives  a  certain  amount  of  it. 

Ortlieb  and  Muller's  Process. — The  process  of  the  Societe  anonyme 
de  Croix  is  due  to  Ortlieb  and  Muller,  and  is  based  on  an  old  reac- 
tion pointed  out  by  Wurtz  (Ann.  de  Chim.  et  Phys.  XXX,  p.  454), 
which  is  as  follows:  If  trimethylamine  be  passed  through  a  porce- 
lain tube  heated  to  redness,  there  is  formed  hydrocyanic  acid  and 
ammonium  cyanide. 

Ortlieb  and  Muller's  process  is  simply  the  application  of  the 


MANUFACTURE  OF   CYANIDES.  191 

above  reaction.  Commercial  trimethylamine  is  first  vaporized  in 
specially  constructed  boilers.  These  vapors  are  then  conducted 
into  retorts  similar  to  those  used  in  gas  manufacture,  and  heated 
to  redness,  when  they  are  broken  up  into  hydrocyanic  acid  and 
ammonium  cyanide.  The  products  of  this  de  omposition  are  con- 
ducted through  a  series  of  absorption  apparatus.  The  first  series 
contains  dilute  sulphuric  acid.  The  ammonium  cyanide  is  there 
decomposed  into  sulphate  of  ammonia,  which  remains  in  solution, 
and  hydrocyanic  acid,  which  together  with  that  already  formed 
in  the  gaseous  mixture,  passes  on  into  the  other  absorbers.  These 
contain  either  sodium  or  potassium  hydrate,  or  milk  of  lime,  or  any 
other  alkaline-earth  hydrate. 

The  alkaline  solutions  absorb  the  hydrocyanic  acid,  yielding 
concentrated  solutions  of  the  corresponding  cyanides,  while  the 
residual  combustible  gases,  completely  freed  from  prussic  acid  and 
ammonia,  are  collected  in  a  gasometer  and  used  as  a  source  of 
illumination.  This  process  allows  the  recovery,  in  the  form  of 
ammonium  sulphate  and  cyanide,  of  the  whole  of  the  nitrogen  of 
trimethylamine. 


CHAPTER  VII. 
MANUFACTURE  OF  FERROCYANIDES. 

FERROCYANIDE  of  potash,  or  yellow  prussiate  of  potash,  has  long 
been,  together  with  Prussian  blue,  the  only  cyanide  compound 
known  and  manufactured.  It  served  a  long  time  as  the  basis  for 
the  manufacture  of  cyanides,  and  at  the  present  time  50%  of  the 
ferrocyanide  produced  is  still  used  for  that  purpose  by  means 
of  the  processes  which  were  reviewed  at  the  beginning  of  Part  I. 

Ferrocyanide  may  be  produced  in  an  industrial  way  by  two 
distinct  classes  of  processes: 

(1)  Those  based  on  the  use  of  nitrogenous  organic   substances. 

(2)  Those  which  utilize  the  spent  oxides  from  the  purification 
of  illuminating-gas,  or  those  whose  object  is  to  extract  the  cyanide 
compounds  directly  from  this  gas. 

Other  processes  have  been  likewise  proposed.  But  most  of 
them  produce  cyanides  as  intermediary  compounds,  and  they  have 
been  studied  in  the  previous  chapter.  It  should  also  be  mentioned 
that  all  the  synthetic  processes  proposed  for  the  production  of 
cyanides  may  likewise  be  employed  in  the  manufacture  of  ferro- 
cyanides,  either  by  adding  metallic  iron  to  the  cyaniding  substances 
or  by  treating  the  cyanided  masses  with  strong  solutions  of  ferrous 
salts. 

The  present  chapter  will  consist  of  two  parts: 

(1)  Manufacture  of  ferrocyanides  by  means  of  nitrogenous  sub- 
stances. 

(2)  Manufacture  of  ferrocyanides  by  means  of  illuminating-gas 
or  of  the  masses  which  have  served  in  its  purification. 

192 


MANUFACTURE  OF  FERROCYANIDES.  193 


I.  OLD  PROCESSES   BASED  ON  THE  USE  OF  NITROGENOUS 
ORGANIC  SUBSTANCES. 

These  processes  were  for  a  long  time  the  only  ones  employed  in 
the  manufacture  of  potassium  ferrocyanide.  At  the  present  time 
they  have  almost  wholly  been  abandoned,  there  being  but  a  few 
works  (in  Germany,  England,  and  the  United  States)  still  in  oper- 
ation. However,  as  many  important  studies  and  investigations 
have  been  conducted  along  the  line  of  these  processes,  and,  more- 
over, as  the  industry  of  the  cyanide  compounds  is  derived  from 
them,  we  shall  describe  them  more  or  less  at  length. 

They  consist,  practically,  in  igniting  nitrogenous  organic  sub- 
stances in  the  presence  of  potassium  carbonate  and  charcoal.  Under 
these  conditions  (without  entering  at  present  into  the  discussion  of 
the  reactions  which  take  place  in  this  formation)  there  is  formed 
potassium  ferrocyanide  through  the  union  of  the  four  elements — iron 
nitrogen,  carbon,  and  potassium: 

Fe(CN)6K4. 

The  discovery  of  ferrocyanide  proceeds  from  that  of  Prussian 
blue;  but  it  came  about  much  later.  It  is  known  that  Prussian 
blue,  discovered  by  Dippel,  was  prepared  by  the  ignition  of  dried  beef- 
blood  in  the  presence  of  potassium  carbonate,  the  mass  thus  obtained, 
on  treatment  with  water,  giving  a  solution  known  as  "blood-lye," 
which  when  treated  with  an  iron  salt  yielded  Prussian  blue.  For 
a  long  time  the  composition  of  "blood-lyes"  was  unknown. 

In  1752,  Macquer  succeeded  in  regenerating  this  product  by 
treating  Prussian  blue  with  an  alkali,  and  his  ideas  concerning  the 
nature  of  this  reaction  led  him  to  give  it  the  name  of  phlogisticated 
alkali. 

Toward  1780,  Sage,  and  later  Bergmann,  successively  established 
that  these  "blood-lyes"  yielded  on  concentration  and  crystallization 
a  definite  body,  to  which  they  gave  the  name  of  "blood-lye"  salt, 
a  name  which  it  held  for  a  long  time. 

It  was  not  until  1823,  thanks  to  the  remarkable  researches 
of  Gay-Lussac,  that  the  composition  of  this  salt  was  known,  which 
is  ferrocyanide  or  cyanoferride  of  potassium,  more  commonly  called 


194      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

yellow  prussiate  of  potash.    Such  was  the  beginning  of  its  manu- 
facture. 

As  a  rule,  all  nitrogenous  organic  substances,  whether  of  vegetable 
or  of  animal  origin,  may  be  utilized  for  the  preparation  of  ferro- 
cyanide.  But,  as  has  already  been  remarked,  these  substances 
almost  always  possess  a  considerable  value  because  they  may  be 
employed  either  in  feeding  or  in  domestic  economy.  They  are 
too  expensive.  Therefore  the  yellow  prussiate  industry  makes 
use  of  the  residues  or  waste  products  the  value  of  which  is  much 


We  have  seen  that  at  first  dried  beef -blood  was  used.  In  1724 
Brown  proposed  to  substitute  for  it  meat,  and  finall  in  1725,  Geffroy 
made  use  of  wool  wastes  and  hartshorns. 

The  organic  substances  used  in  the  maunfacture  of  yellow  prus- 
siate may  be  divided  into  five  classes:  hair,  rags,  horn,  leather,  and 
tendons. 

Under  the  term  horn  are  included  hoofs,  the  claws  of  animals, 
points  of  horns,  defective  horns,  the  wastes  from  the  manufacture  of 
combs,  buttons,  etc. 

Hair  and  rags,  which  are  often  put  in  the  same  class,  include 
bristles  of  swine  and  hair  unfit,  for  the  manufacture  of  the  various 
kinds  of  brushes,  wool  wastes,  the  hair  of  domestic  animals,  the 
wastes  of  woolen  cloth  which  cannot  be  used  in  paper-making, 
damaged  cloth,  and  the  trash  obtained  in  trimming  cloth,  generally 
called  shearings. 

Leather  may  be  divided  into  two  groups: 

(1)  The  wastes  or  clippings  of  new  leather,  i.e.,  the  wastes  of 
harness-shops,  morocco-leather  manufactories,  shoe-shops,  tanneries. 

(2)  Old  leather,  more  commonly  called  old  shoes. 

Red  leather  is  to  be  preferred,  chamois  leather  is  rarely  used, 
and  white  leather  never.  The  wastes  of  kid-glove  manufactories 
cannot  be  used  on  account  of  the  presence  of  alum. 

By  tendons  it  is  understood  the  slaughter-house  detritus,  certain 
portions  of  dead  animals,  and  the  dried  muscles  of  these  same  animals. 

The  composition  of  these  different  products  depends  upon  the 
circumstances  inherent  in  the  treatment  to  which  they  have  been 
subjected,  or  upon  the  condition  in  which  they  have  been  found. 

Three  essential  elements  must  be  taken  into  consideration  in 


MANUFACTURE  OF  FERROCYANIDES.  195 

the  substances  used  for  the  manufacture  of  ferrocyanide,  viz.,  the 
percentage  of  nitrogen,  of  sulphur,  and  the  amount  of  ash. 

Upon  the  richness  in  nitrogen  depends  the  value  of  these  sub- 
stances and  therefore  the  yield  in  prussiate.  This  is  therefore  of 
first  importance.  As  to  the  other  two  elements,  they  are  interesting 
only  so  far  as  they  exert  a  detrimental  action  on  the  yield. 

In  fact,  in  proportion  as  these  two  elements  are  present  is  the 
percentage  of  nitrogen  less.  Moreover,  the  sulphur  may  unite  and 
form  sulphocyanide,  which  reduces  by  so  much  the  yield  of  ferro- 
cyanide. This  objection  may  be  avoided  by  adding  iron  to  the 
mass;  the  iron  sulphide  formed  will  be  converted  into  ferrocyanide 
when  the  mass  is  lixiviated.  The  composition  of  the  ash  should  be 
taken  into  consideration;  phosphoric  acid  and  silica  exert  a  detri- 
mental action  on  the  formation  and  crystallization  of  ferrocyanide. 

The  following  table  gives  the  composition  of  the  nitrogenous 
organic  substances  most  generally  used  in  the  manufacture  of  ferro- 
cyanide. 

It  should  be  mentioned,  as  will  be  seen  on  examining  the  table, 
that  the  organic  substances  contain  three  times  as  much,  and  some- 
times more,  carbon  as  nitrogen,  while  yellow  prussiate  contains 
these  two  elements  in  about  equal  proportions  (116  of  carbon,  120 
of  nitrogen). 

The  nitrogenous  organic  substances,  when  subjected  to  ignition^ 
lose  i  of  their  nitrogen  in  the  form  of  ammonia  or  ammoniacal  com- 
pounds at  a  temperature  below  that  of  the  formation  of  cyanide. 

Thus,  these  substances  are  often  subjected  to  a  previous  ignition 
at  a  low  heat,  during  which  the  ammoniacal  products  set  free  are 
collected.  The  residue  is  animal  charcoal,  containing  the  rest  of  the 
nitrogen.  The  percentage  of  nitrogen  itself  varies,  depending  upon 
the  process  of  ignition,  the  percentage  decreasing  with  the  increase  of 
temperature  of  ignition.  In  general  one  seeks  to  produce  a  charcoal 
containing  4-5%  nitrogen,  which  corresponds  to  about  a  f  diminution 
of  the  mass. 

This  ignition  takes  place  in  cast-iron  boilers  1  meter  high  and  1 
meter  in  diameter  the  cover  of  which  is  provided  with  .an  exit  tube 
connected  with  an  apparatus  which  serves  for  the  absorption  of  the 
ammoniacal  compounds.  Since  the  bottom  wears  away  so  rapidly 
it  is  so  arranged  that  it  may  easily  be  replaced. 


196       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 


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MANUFACTURE  OF  FERROCYANIDES.  ,       197 

The  second  raw  material  in  the  manufacture  of  yellow  prussiate  is 
potash.  Generally  commercial  potassium  carbonate  is  used,  which 
often  contains  other  salts  such  as  sulphate,  silicate,  chloride  of 
potassium,  and  sometimes  sodium  salts.  The  chlorides  exert  no 
influence;  the  sulphates  form  sulphides  during  the  process,  which 
attack  the  cast  metal  and  rapidly  puts  the  apparatus  out  of  service. 
The  silicates  and  earthy  substances  likewise  exert  an  injurious  action. 

One  may  likewise  use  blue  potash  extracted  from  the  mother- 
liquors  of  a  previous  manufacture,  a  product  which  contains  40-90% 
potash,  but  4-8%  potassium  sulphide,  7-16%  potassium  silicate, 
7-13%  potassium  chloride.  It  is  therefore  necessary  to  subject 
these  substances  occasionally  to  purification,  for  their  coefficient  of 
impurities  increases  with  the  successive  number  of  ignitions. 

The  iron,  which  is  often  added  to  the  ignition,  may  be  used  in 
the  metallic  form  (nails,  filings,  wastes  from  tin-plate),  or  oxid 
(forge  scales),  which  becomes  reduced  at  the  beginning  of  the  igni- 
tion. The  forge  scales  are  often  objectionable  because  they  contain 
a  large  amount  of  combined  silica,  and  earthy  matters. 

The  manufacture  of  potassium  ferrocyanide  Comprises  three 
distinct  stages: 

1.  Ignition  or  production  of  the  metal. 

2.  Lixiviation  of  the  metal. 

3.  Crystallization. 

i.  Ignition  or  Production  of  the  Metal. — By  the  name  metal 
is  meant  the  crude  product  resulting  from  the  ignition  of  the  nitrog- 
enous organic  substances  in  the  presence  of  iron  and  alkali. 

The  amount  of  these  raw  materials  to  be  used  is  as  follows: 

Carbonate  of  alkali.  . 100     parts 

Nitrogenous  substances  (130-140   at  a  maximum,  170 

with  animal  black) 125        "' 

Metallic  iron r 6  or  7    " 

The  whole  mixture  of  these  substances  may  be  charged  in  retorts 
or  ovens,  but  it  is  much  better  first  to  add  the  potash,  then  to  shovel 
in  the  animal  substances. 

In  fact,  under  the  influence  of  the  high  temperature  necessary 
to  carry  on  the  reaction,  an  abundant  liberation  of  combustible 
gases  is  produced  (carbon  monoxid,  carbides,  carbonic  acid),  which 


198       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

remove  from  the  mass  a  large  amount  of  heat.  The  successive 
additions  of  animal  substances  to  the  mass  restore  to  it  the  amount 
of  heat  lost.  To  carry  on  the  reaction  in  the  best  way,  it  is  necessary 
that  the  temperature  be  always  sufficiently  high  that  the  alkali 
carbonate  may  be  reduced  by  the  charcoal,  but  it  should  not  be 
too  high,  otherwise  some  of  the  cyanide  formed  will  be  volatilized. 

The  operation  takes  place  in  iron  kettles,  or  in  specially  con- 
structed retorts,  or  in  reverberatory  furnaces. 

The  oldest  apparatus  known  is  pear-shape  (Fig.  17).  This 
oval  or  pear-shaped  retort  (A)  is  of  iron  and  rests  on  one  side,  on 


FIG.  17. — Pear-shaped  Retort  for  the  Manufacture  of  Ferrocyanide. 

A,  retort;   D,  fire-grate;    C,  vault;   E,  flue  for  the  outlet  of  gases;    B,  opening 
for  charging  and  unloading;  G,  kettle  for  the  evaporation  of  the  strong  solutions. 

the  stonework  of  the  oven,  by  means  of  a  powerful  trunnion,  and 
on  the  other,  on  the  facade  wall  of  the  oven  by  its  neck.  It  thus 
presents  a  slight  inclination  backward.  It  is  1.20  meters  long, 
0.80  meter  in  diameter,  and  0.15  meter  thick.  The  rounded 
part  of  the  retort  is  free,  and  is  completely  exposed  to  the  action 
of  the  flame  which  arises  from  the  grate  D.  The  opening  B,  which 


MANUFACTURE   OF  FERROCYANIDES. 


199 


serves  to  load  and  unload  the  retort,  is  closed  by  a  sheet-iron  lid. 
The  products  of  combustion,  coming  from  the  fire-grate  D,  are 
distributed  on  each  side  of  the  retort,  and  again  come  together 
in  the  arch  C  and  escape  by  means  of  the  flues  E.  The  heat  lost 
from  these  gases  is  utilized  in  evaporating  the  strong  solutions  in 
the  vessel  G.  The  retort  A  may  be  turned  over  from  time  to  time 
in  order  to  change  the  surface  coming  in  direct  contact  with  the 
flame  and  to  avoid  a  too  rapid  wear  and  tear.  There  are  two  objec- 


FIG.  18. — Reverberatory  Furnace. 

tions  to  this  class  of  apparatus:  they  wear  out  very  rapidly,  and 
the  action  of  the  heat  may  be  exerted  on  the  substances  only  through 
the  walls  of  the  retort. 

The  pear-shaped  retort  has  been  replaced  by  the  reverberatory 
furnace.  The  sole  of  this  furnace  consists  of  a  cast-iron  cupel  (7 
(Fig.  18)  1.1  meters  in  diameter  and  0.10  meter  thick.  The  fuel  is 
put  on  the  grate  B,  the  products  of  combustion  follow  the  conduit  E 
in  the  direction  indicated  by  the  arrow,  and  come  to  the  vault  A, 
where  they  heat  the  cyaniding  mixture  from  above,  and  in  this 
way  the  high  temperature  necessary  for  the  reaction  is  more  easily 
attained. 


200       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

In  some  works  the  gases  of  the  grate  pass  under  the  cupel 
before  coming  in  contact  with  the  surface  of  the  mixture.  On  com- 
ing out  of  the  vault  A  the  gases  .pass  through  a  lateral  tube  and 
thence  through  the  chimney  F,  whence  they  are  conducted  under 
evaporating-kettles  which  they  heat. 

In  these  furnaces  500  kg.  of  material  may  be  converted  at  one 
time  into  yellow  prussiate.  The  cupels  wear  out  rapidly,  but 
can  easily  be  replaced;  thus,  after  700  tappings,  a  1500  kg.  cupel 
will  weigh  no  more  than  250  kg.,  and  should  not  be  used  fur- 
ther. The  wear  and  tear  is  particulary  rapid  in  the  case  of  fur- 
naces with  double  circulation,  where  the  combustion  gases  pass 
above  and  below  the  cupel.  These  furnaces  have  been  used  quite 
extensively  in  Germany. 

The  operation  is  as  follows:  The  cupel  is  first  heated  to  red- 
ness. When  this  is  done,  the  inlet  of  gases  is  shut  off  and  the  mix- 
ture of  potassium  carbonate  and  blue  potash  is  introduced  into 
the  cupel,  and  the  cover  closed.  The  gases  are  let  on  again  and 
the  mass  brought  to  fusion.  When  this  is  in  perfect  fusion,  the 
poker  is  introduced  and  the  nitrogenous  substances  shovelled 
in,  mixing  them  in  the  mass  with  the  aid  of  the  fire-iron.  A  lively 
reaction  takes  place,  accompanied  by  effervescence  and  an  abun- 
dant liberation  of  combustible  gases  which  burn  at  the  surface  of 
the  bath  with  flames  sometimes,  2  meters  in  length. 

To  prevent  the  fused  mass  from  overflowing,  small  portions  of 
nitrogenous  substances  are  added  whenever  the  reaction-  becomes 
too  lively.  When  about  half  'of  the  nitrogenous  substances  has 
been  added,  the  reaction  becomes  more  gentle;  further  addition  is 
stopped  for  V2-8/4  of  an  hour,  during  which  time  the  mass  is  vigor- 
ously stirred  with  the  poker  until  the  bath  is  completely  fluid.  The 
rest  of  the  organic  substance  is  then  added  in  2  or  3  portions.  All 
these  operations  require  about  2  hours.  The  mass  is  again  heated 
for  l/2  hour,  after  which  it  has  the  appearance  of  a  thick  liquid, 
and  is  run  into  moulds  with  the  help  of  an  iron  spoon.  After  cool- 
ing, it  has  the  appearance  of  loaves  of  bread.  As  a  rule,  6  tappings 
of  250  kg.  each  may  be  made  for  each  furnace  every  24  hours;  but, 
of  course,  the  length  of  the  operation  varies  according  to  the  nature 
of  the  substances  acted  upon,  the  intensity  of  the  fire,  the  experi- 


MANUFACTURE  OF  FERROCYANIDES.  201 

ence  of  the  workman  using  the  poker,  etc.    In  any  case  it  varies 
from  4  to  6  hours. 

In  England,  preference  was  given  to  vertical  cast-iron  boilers, 
slightly  narrowed  at  the  opening  and  provided  with  a  mechanical 
stirrer  whose  axle  penetrated  the  cover,  and  set  in  motion  by  means 
of  gears  connected  with  the  source  of  power.  This  arrangement 
allowed  a  good  deal  of  manual  labor  to  be  spared.  Generally  these 
boilers  were  arranged  in  series  of  24. 

Although  this  method  has  certain  advantages,  it  has  great  dis- 
advantages. The  greatest  objection  consists  in  the  losses,  which 
are  appreciable,  due  to  the  fact  that  the  nitrogenous  substances 
float  on  the  surface  of  the  bath  and  there  burn,  the  nitrogenous 
gases  liberated  thereby  coming  in  contact  with  but  a  thin  layer 
of  potash  and  thus  escape  without  being  combined. 

Engler's  process  has  the  object  in  view  of  obviating  this  diffi- 
culty by  causing  the  nitrogenous  gases  to  become  liberated  in 
the  very  midst  of  the  mass  itself. 

Engler's  Apparatus. — This  consists  of  a  vertical  boiler  60  centi- 
meters in  diameter  and  2  meters  high.  A  piston,  formed  by  a  per- 
forated sheet-iron  disc  and  moved  to  and  fro,  continually  rams  the 
nitrogenous  substances  into  the  very  mass  itself.  First,  300  kilo- 
grams of  potassium  carbonate  are  placed  in  the  boiler;  when  this 
is  melted  small  portions  at  a  time  of  nitrogenous  substances  are 
added  through  the  hopper  (the  piston  being  lowered),  till  the 
whole  of  the  nitrogenous  substances  has  been  added.  The  unload- 
ing is  done  from  beneath,  and  the  mass  is  collected  in  a  suitable 
truck.  The  ammonia  set  free  during  the  reaction  is  collected  in 
a  tower  filled  with  pieces  of  coke. 

The  product  of  ignition  obtained  in  either  one  of  the  processes 
just  described  is  a  greenish-black  mass,  quite  hard,  porous,  absorb- 
ing atmospheric  moisture  energetically,  with  liberation  of  ammonia 
and  hydrocyanic  acid.  This  is  the  mass  which  is  commonly  called 
metal.  It  yields  about  16%  potassium  ferrocyanide.  Its  compo- 
sition varies,  of  course,  with  the  composition  of  the  substances  used, 
the  length  of  the  operation,  and  the  method  used  in  carrying  it  on. 

Karmrodt,  who  took  the  average  of  ten  tappings,  produced  by 
igniting  100  parts  of  potash,  100  parts  nitrogenous  material,  and 
10  of  iron,  gives  the  following  figures: 


202       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

Cyanide  of  potash 8 . 20 

Sulphocyanide  of  potassium 3 . 33 

Cyanate  of  potassium 2 . 46 

Carbonates  of  sodium  and  potassium 57. 56 

Sulphate  of  potassium 2 . 82 

Silica 3.10 

Insoluble.  .  .  * 18. 11 

Undetermined.  .  4.42 


100.00 

As  may  be  seen,  the  metal  does  not  contain  any  ferrocyanide. 
This  salt  is  formed  only  on  lixiviation. 

The  metal  is  broken  into  lumps  as  large  as  one's  fist  and  thrown 
into  vats  containing  water  or  weak  solutions  from  a  previous  opera- 
tion; this  is  heated  to  60-90°  for  12  to  14  hours  while  stirring. 
The  temperature  should  not  exceed  90°,  nor  be  kept  at  that  point 
too  long,  for  the  cyanide  might  be  converted  into  ammonia  and 
potassium  formate. 

When  all  the  solid  pieces  have  disappeared  and  the  solution 
-shows  about  24°  B.,  it  is  allowed  to  stand  3  or  4  hours,  after  which 
the  clear  liquid  is  decanted.  The  residue  is  washed  with  fresh 
water,  the  washings  being  used  in  lixiviating  the  succeeding  metal. 

The  clear  liquid  or  "  blood-lye,"  which  is  greenish  black  in  color, 
is  concentrated  in  kettles  by  the  waste  heat  from  the  ignition  furnaces 
until  the  solution  shows  32°  B.  It  is  finally  run  into  wooden  crys- 
tallizing vats,  where  it  deposits  on  cooling  a  grayish  crystalline 
product,  called  crude  salt,  containing  about  1/6  of  its  weight  of  fer- 
rocyanide of  potassium. 

This  crude  salt  is  withdrawn  and  placed  in  wicker-baskets  in 
order  to  drip.  It  is  purified  by  a  second  and  sometimes  a  third 
*  crystallization.  The  final  product  is  a  lemon-colored  salt — potassium 
lerrocyanide,  Fe(CN  6K4+3H20. 

When  th  mother-liquors  are  concentrated  to  40°  B.  a  fresh 
quantity  f  very  small  crystals  appears,  which  are  purified  by 
repeated  crystallization. 

Gentele  avoids  the  second  crystallization  by  precipitating  the 
ferrocyanide  completely  from  its  solution  at  the  boiling-point.  The 
lyes  at  35°  B.  are  heated  to  boiling.  Under  these  conditions  the 


MANUFACTURE  OF  FERROCYANIDES.  203 

salt  is  deposited;  this  is  withdrawn  and  allowed  to  drip.  When  the 
lyes  show  50°  B.,  the  boiling  is  stopped  and  the  lyes  allowed  to 
stand  overnight,  when  the  rest  of  the  cyanide  is  deposited.  In 
this  way  no  very  small  or  "fat"  crystals  are  obtained;  the  mother- 
liquors  are  treated  directly  in  order  to  obtain  the  blue  potash.  Gen- 
tele's  method  of  obtaining  the  crude  salt  yields  somewhat  more 
potassium  sulphate  than  the  ordinary  method. 

It  remains  but  to  purify  the  crude  salt  obtained  by  either  of 
these  two  methods;  to  this  end,  it  is  dissolved  in  just  enough  hot 
water  so  that  the  solution  shows  32°  B.  It  is  allowed  to  stand  and 
is  then  drawn  off  or  filtered  in  order  to  separate  the  black  par- 
ticles of  insoluble  residue  which  detract  from  the  appearance  of 
the  product.  The  clear  solution  is  then  transferred  to  rather  deep 
wooden  or  sheet-iron  crystallizing  vats  which  are  surrounded  by 
insulating  bodies,  where  it  is  left  during  8-10  days.  The  ferro- 
cyanide  is  deposited,  the  mother-liquors  being  drawn  off  carefully 
and  used  to  dissolve  a  fresh  amount  of  crude  salt,  while  the  crys- 
tals are  covered  over  with  a  new  solution  sufficiently  concentrated 
to  add  to  the  crystals  already  deposited.  This  is  repeated  until 
the  crystals  obtained  are  10-12  cm.  in  length  In  fact,  commerce 
seeks  rather  to  have  large  and  regular  crystals  than  pure  ones. 
The  crystals  are  removed,  washed  with  a  small  amount  of  water, 
and  dried. 

Sometimes  the  salt  is  crystallized  in  groups  by  suspending  crystals 
to  threads  tied  to  wooden  rods  placed  in  the  crystallizing- vats. 

As  to  the  very  fine  crystals,  they  are  dissolved  in  water,  and, 
after  concentrating  the  solution  to  30°  B.,  allowed  to  crystallize; 
the  salt  thus  obtained  is  added  to  the  crude  salt  and  treated  as 
such.  The  mother  liquors,  evaporated  to  40°  B.,  yield  pearly  crystals 
of  a  double  salt  of  cyanide  and  chloride  of  potassium,  much  used 
in  the  manufacture  of  alum. 

The  refined  salt  is  never  pure:  it  always  contains  a  little  potas- 
sium sulphate  which  is  difficult  to  get  rid  of.  Yet  one  may  obtain 
it  free  from  sulphate  by  dissolving  the  salt  in  water  and  concen- 
trating the  solution  to  the  density  1.31.  At  this  point  the  greater 
part  of  the  sulphate  of  potash  separates  out.  Water  is  then  added 
to  bring  the  density  to  1.27  and  the  solution  allowed  to  crystallize. 
This  is  done  but  rarely,  for  the  presence  of  potassium  sulphate  does 


OF  THE 

UNIVERSITY 

OF 


204      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 


not  in  any  way  interfere  with  the  industrial  use  of  potassium  ferro- 
cyanide,  the  only  objection  being  that  it  reduces  by  just  so  much 
the  amount  of  useful  cyanogen. 

The  manufacture  of  potassium  ferrocyanide  leaves  behind  two 
important  residues:  a  black  mass  and  blue  potash. 

The  black  mass  is  made  up  of  the  residue  from  lixiviating  the 
metal.  It  is  friable  and  of  a  composition  varying  according  to  the 
nature  of  the  organic  substances  used  and  the  method  of  procedure 
It  consists  to  a  large  extent  of  carbon  and  mineral  substances- 
silicates,  phosphates,  chlorides,  sulphides,  soda,  potash,  lime,  etc. 

In  the  following  table  Karmrodt  gives  the  analyses  of  three 
samples  of  this  black  mass: 


Substance. 

Horn. 

Leather. 

Rags. 

Charcoal          

Per  Cent. 
6   10 

Per  Cent. 
9.19 

Per  Cent. 
4  22 

Potash  

12.18 

10.22 

16.70 

Lime  

16.20 

19.66 

18.45 

Majrnesia 

2  15 

0  97 

1  27 

Sesquioxid  and  metallic  iron  
\lumina        

16.14 
4  80 

3.10 
14  17 

2.12 
10  24 

Manganese  

0.42 

0  72 

0  06(?) 

Copper 

trace 

0  .  02  (?) 

0.42 

Silica 

21  14 

26  45 

29  70 

Sulphuric  acid 

1  27 

1  85 

0  16 

Phosphoric  acid 

10  45 

4  92 

6  44 

Residue  :  Sulphur,  CO2;  chlorine,  CN 

9.15 

8.73 

10.22 

100.00 

100.00 

100.00 

The  amount  of  the  black  mass  varies  according  to  the  substances 
used.  Karmrodt  found  the  following: 

Using  wool  wastes 28. 3% 

"     horn 18.7 

"     hair. 23.0 

"     leather  scraps 35. 0 

It  is  sold  mostly  as  a  fertilizer,  due  to  its  high  content  of  potash 
and  phosphoric  acid.  In  order  to  recover  the  potash  (9%),  vari- 
ous uses  have  been  attempted,  especially  that  of  utilizing  it  in  the 
manufacture  of  alum,  but  the  experiments  thus  undertaken  were 
not  successful  owing  to  the  fact  that  the  labor  cost  more  than  the 
value  of  the  product. 


MANUFACTURE  OF  FERROCYANIDES. 


205 


Blue  potash  is  the  residue  after  evaporating  to  dryness  the 
mother-liquors  obtained  from  the  crystallization  of  the  crude  salt. 
It  contains  potash  in  excess  in  the  free  state  or  in  the  form  of  salts 
not  combined  with  cyanogen,  and  the  salts  supplied  by  the  ash, 
It  is  used  again  in  the  process,  mixed  with  fresh  potash.  Its 
composition  varies  according  to  the  number  of  ignitions  to  which 
it  has  been  subjected.  It  is  evident  that  it  becomes  more  and  more 
impure,  and  ends  by  becoming  useless. 


Hoffmann. 

Brunquell. 

Karmrodt. 

Potassium  carbonate.  .  . 
'  '          silicate.    .  .  . 

44.1  to  84.0 
7.  6  to  20.4 

71.9 

11.9 

52.75 
16.57 

Sulphide  

1.4to    8.8 

4.3 

6  18 

Chloride       

7.2to  13.1 

1.15 

Phosphate 

2  04 

Sulphate 

4  34 

Potash                

7  22 

Ferrocyanide  

2  84 

Sulphocyanide        

trace 

Insoluble  residue  
Other  substances  
Water 

1        26.77     j 

1.6 
8.2 
2  1 

3.86 
3.07 

Theory  of  the  Manufacture  of  Potassium  Ferrocyanide  by  the 
Old  Process.  —  Seyeral  hypotheses  have  been  proposed  on  this  sub- 
ject, the  first  and  most  probable  of  which  is  the  following: 

Nitrogenous  organic  substances  contain  carbon,  nitrogen,  hydro- 
gen, and  oxygen.  After  ignition,  they  still  contain  all  these  elements 
except  oxygen  and  a  large  part  of  the  nitrogen  which  is  volatilized  in 
the  form  of  ammonia.  Now  as  the  amount  of  carbon  in  these  sub- 
stances is  much  larger  than  that  of  nitrogen,  it  follows  that  only  a 
part  of  this  carbon  enters  into  combination  with  the  nitrogen  in  order 
to  yield  cyanogen, 


and  the  rest  of  the  carbon  reacts  upon  the  carbonate  of  potash, 
which  it  reduces,  thus  setting  the  metal  free, 


=  C02+CO+K2, 


206       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

which  metal,  reacting  upon  the  cyanogen  formed,  unites  with  it  and 
produces  potassium  cyanide, 

CN+K  =  CNK. 

» 

As  may  be  seen,  iron  seems  to  take  no  part  in  this  reaction,  and  yet 
it  is  indispensable  that  some  be  put  in.  In  fact,  carbonate  of  potash 
always  contains,  besides  other  impurities,  a  small  amount  of  sulphate 
of  potash.  In  contact  with  carbon,  this  salt  becomes  likewise 
reduced,  yielding  potassium  sulphide, 

S04K2  +  4C  =  K2S+4CO, 

and  this  sulphide,  in  the  presence  of  the  cyanide  formed,  yields 
sulphocyanide. 

The  object  of  the  iron  is,  therefore,  to  absorb  the  sulphur  of  the 
potassium  sulphide,  forming  insoluble  iron  sulphide, 

K2S+Fe=FeS+K2, 
or 

K2S  + Fe + 2C  +  2N  = FeS  +  2CNK, 

which  entirely  prevents  the  formation  of  sulphocyanide,  the  forma- 
tion of  which  must,  under  all  circumstances,  be  avoided  in  the 
manufacture  of  potassium  ferrocyanide. 

Therefore  the  product  after  igniting  the  raw  materials  (nitrog- 
enous subst  nces,  carbonate  of  potash,  iron),  otherwise  called  the 
metal,  will  be  a  rather  complex  mixture  which  may  contain: 

Potassium  cyanide; 

Alkali  carbonate  in  excess; 

Undecomposed  organic  substances; 

Iron  ; 

Iron  sulphide; 

Carbon. 

It  should  be  stated  that  we  do  not  include  the  presence  of  potas- 
sium ferrocyanide  in  the  said  mixture.  It  is,  in  fact,  admitted, 
according  to  actual  data,  that  this  salt  is  formed  only  at  the  time  of 
lixiviation  in  the  following  way: 


MANUFACTURE  OF  FERROCYANIDES.  207 

During  lixiviation,  potassium  cyanide  reacts  with  sulphide  of 
iron,  yielding  potassium  ferrocyanide  according  to  either  of  the 
following  reactions: 

2CNK+Fe  =  (CN)2Fe+K2 
4CNK  +  (CN)2Fe  =  Fe(CN)6K4, 

or 

2CNK + FeS  -  (CN)2Fe  +  K2S 
(CN)2Fe  +4CNK  =  Fe(CN)6K4, 

or 

6CNK  +  FeS  =  K2S + Fe(CN)6K4. 

That  is  precisely  the  reason  why  one  should  not  think  of  extracting 
directly  by  lixiviation  the  potassium  cyanide  formed  in  the  "metal." 
Still  another  theory  is  the  following:*  The  reason  for  igniting 
organic  substances  is  to  produce  a  nitrogenous  charcoal  which 
would  react  with  the  potassium  carbonate,  yielding,  in  all  proba- 
bility, acetylene.  In  its  turn  the  acetylene  would  react  with  the 
potassium,  set  free  from  potassium  carbonate,  and  with  the  ni- 
trogen of  the  organic  substance,  or,  in  case  of  need,  with  nitrogen 
of  air,  thus  yielding  potassium  cyanide,  as  follows: 

C2H2 + K2 + N2  =  2CNK  +  H2. 

It  is  just  at  this  point  that  the  presence  of  iron  would  cause  the 
formation,  first  of  cyanide  of  iron,  then  of  potassium  ferrocyanide, 
according  to  the  reactions  above  indicated. 

Yield. — The  yield  obtained  by  igniting  nitrogenous  organic 
substances  depends  on  several  conditions. 

From  many  experiments  on  a  large  scale  made  by  Karmrodt,  it 
follows  that  the  yield  may  vary  from  10-18%  of  the  weight  of  the 
salt  used. 

As  an  average  of  459  different  operations,  Fleck  places  the  yield 
at  11%. 

Hoffmann  studied  the  various  conditions  which  may  influence 
the  yield,  the  following  being  the  result  of  his  investigations: 

(1)  The  nature  of  the  nitrogenous  organic  substances  exerts  a 

*  Prunier,  Medicaments  chimiques,  Vol.  I. 


208       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

considerable  influence  on  the  yield  of  cyanide  and  of  sulphocyanide; 
it  is,  however,  impossible  to.  establish  a  fixed  relation  between  the 
yield  and  the  nitrogenous  content  of  the  organic  substances  used. 

(2)  The  formation  of  potassium  cyanide 'is  quite  closely  pro- 
portional to  the  weight  of  organic  substances. 

(3)  The  yield  seems  to  increase  with  the  purity  of  the  alkali. 

(4)  The  yield  increases  especially  with  the  temperature. 

(5)  It  increases  more  rapidly  still  if  for  a  like  quantity  of  potash 
the  addition  of  organic  substances  be  increased. 

(6)  If  blue  potash  be  employed,  the  amount  of  black  mass  is 
twice  as  great  as  if  pure  potash  had  been  used. 

(7)  For  the  same  amount  of  potassium  ferrocyanide  produced, 
the  amount  of  pure  potash  consumed  depends  on  the  nature  of  the 
organic  substances. 

(8)  The  comsumption  of  organic  substances  is  greater  with  blue 
potash  than  with  pure  potash. 

(9)  The  amount  of  sulphocyanide  formed  does  not  vary  whether 
iron  shavings  or  iron  turnings  be  added  to  the  mixture ;  but  it  decreases 
if  finely  divided  reduced  iron  be  used;   there  is  almost  no  forma- 
tion if  at  the  end  of  the  operation  forge  scales  be  added.     To  these 
theoretical  considerations   should  be  added  the  following,   based 
upon  experimental  data: 

(1)  A  relatively  small  proportion  (Vs-1/?)  of  the  total  nitrogen 
of  the  organic  substances  contributes  to  the  formation  of  the  cyanide. 
The  remaining  4/5  or  6/7  are  lost  or  volatilized  as  ammonia.     A 
certain  amount  is,  however,  retained.     At  the  beginning  of  ignition, 
the  temperature  being  relatively  low,   a  portion  of  the  nitrogen 
escapes  under  the  form  of  ammonia;  but  when  the  temperature  has 
become  raised,  this  ammonia  coming  in  contact  with  carbon  becomes 
converted  into  hydrogen  and  hyrdocyanic  acid,  which  latter  unites 
with  potassium  in  order  to  form  cyanide  of  potassium.     It  follows 
that  if  this  high  temperature  could  be  obtained  from  the  beginning 
of  the  operation,  there  would  probably  be  formation  'of  cyanide 
from  the  first. 

(2)  Just  as  only  a  small  proportion  of  the  total  nitrogen  be- 
comes really  utilized,  so  only  a  fraction  of  the  potash  used  unites 
with  the   cyanogen.     According  to   Karmrodt's   experiments,    this 
amounts  to  l/7-1/io.    It  should,  however,  be  remarked  that  besides 


MANUFACTURE  OF  FERROCYANIDES.  209 

'its  role  of  absorbing  the  cyanogen  formed,  potash  also  acts  as  a 
flux,  the  effect  of  which  is  to  reduce  the  mass  to  a  state  of  liquid 
which  is  absolutely  indispensable  for  the  proper  formation  of  potas- 
sium cyanide.     Part  of  the  potash  is  recovered  in  the  mother-liquors, 
but  a  rather  large  amount  is  volatilized  or  lost  in  the  various  manipu- 
lations.    According  to  Hoffmann  this  loss  may  amount  to  10-20%. 
(3)  Besides  cyanide  of  potassium  there  is  also  formed  during 
ignition  sulphocyanide  of  potassium.     The  formation  of  this  salt 
is  variously  explained.    According  to  some  it  is  due  to  the  presence  of 
potassium  sulphate  in  the  carbonate  used.     Hoffmann  objects  to 
his  hypothesis  because  when   in   his  experiments  he   used  potash 
absolutely  free  from  sulphate,  he  noticed  a    formation  of  sulpho- 
cyanide   to    about    the    same    extent.     These    investigations    led 
to    a  second   hypothesis:   the  influence   of   the  sulphur,  which  is 
present  almost  always  in  animal  substances,  the  amount  reaching 
sometimes  3%.     A  great  portion  of  this  sulphur  is,  however,  vola- 
tilized, the  rest  being  converted   into  sulphocyanide.     In  fact  this 
formation  of  sulphocyanide  constitutes  a  loss  from  the  point  of  view 
of  the  yield  of  ferrocyanide,  a  loss  which  may  amount  to  1/5  of  its 
weight.     It  is  for  the  purpose  of  overcoming  this  objection  that 
iron  is  added,  which  during  the  fusion  reduces  the  sulphocyanide. 
If,  however,  one  succeeds  in  the  laboratory  in  obtaining  a  metal 
free  from  sulphocyanide,  it  is  entirely  different  on  an  industrial 
scale,  in  which  case  a  small  amount  of  this  salt  is  always  found.  N611- 
ner  recommended  the  use  of  chalk,  but  the  results  obtained  with 
this  reagent  .are  not  very  satisfactory.     Forge  scales  give  excellent 
results,  but  they  have  the  great  objection  of  breaking  up  a  portion 
of  the  potassium  cyanide.     All  in  all,  iron  is  the  best  reagent;   it 
also  serves  in  preventing  a  too  rapid  wear  and  tear  of  the  apparatus; 
it  unites  with  the  potassium  sulphide  and  converts  it  into  iron  sul- 
phide, which  does  not  attack  the  walls  of  the  vessels. 

K2S+Fe=FeS+K2. 

(4)  The  reaction  should  not  be  carried  on  too  far,  otherwise 
the  yield  may  decrease  9-12%  (Hoffmann). 

(5)  The  substances  employed  should  all  be  absolutely  dry,  the 
water-vapor  set  free  during  the  reaction  exerting  an  action  which 
decomposes  the  cyanide  formed. 


210       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

Observations  Concerning  Lixiviation  and  Crystallization. — (1)  The 
use  of  iron  protoxid  salts  to  convert  cyanide  into  ferrocyanide  is 
advantageous.  The  carbonate  or  sulphate  of  iron  may  be  used, 
but  generally  in  the  industries  the  use  of  sulphide  of  iron  is  pre- 
ferred. 

(2)  In  evaporating  the  lyes,  it  is  best  not  to  bring  them  imme- 
diately to  the  boiling-point,  otherwise  the  unconverted  cyanide 
of  potassium  woUd  be  decomposed.  The  temperature  should 
not  exceed  70-80°.  Brunquell  recommends  macerating  the  metal 
during  24  hours  at  50-60°. 

The  sum  total  of  these  various  theoretical  and  practical  considera- 
tions shows  well  that  the  manufacture  of  potassium  ferrocyanide 
by  the  old  process  is  filled  with  defects  and  requires  a  great  deal  of 
care  if  a  really  profitable  yield  is  to  be  obtained.  All  in  all,  the 
losses  are  considerable  and  intimately  bound  to  numerous  circum- 
stances. The  chief  objections  to  this  method  may  be  thus  summed  up : 

(1)  Serious  losses  of  nitrogen  through  volatilization  at  the  time 
of  ignition. 

(2)  Loss  of  potash. 

(3)  Loss  of  cyanide  because  of  the  formation  of  sulphocyanide 
and  cyanate. 

(4)  Loss  of  cyanide  due  to  the  incomplete  transformation  of 
this  salt  at  the  time  of  lixiviation. 

(5)  Rapid  wear  and  tear  of  the  apparatus. 

(6)  Heavy  expense  for  fuel. 

It  has  been  sought  to  remedy  these  objections,  and  numerous 
improvements  have  been  applied  to  the  methods  which  we  have  just 
described. 

The  object  of  most  of  them  is  to  utilize,  as  much  as  possible, 
the  nitrogen,  which  at  the  beginning  of  ignition  escapes  from  the 
organic  substances  under  the  form  of  ammonia.  Such  are  the 
processes  of  Brunquell  and  of  Karmrodt. 

BrunquelTs  Process. — This  process  may  be  carried  out  in  two 
different  ways.  » 

In  the  first,  two  iron  retorts  are  used  connected  with  a  vertical 
tube.  The  mixture  of  organic  substances,  potash,  and  iron  prepared 
in  the  ordinary  manner  is  charged  into  the  lower  retort,  while  the 
upper  retort  contains  a  mixture  of  animal  charcoal  and  potash. 


MANUFACTURE  OF  FERROCYANIDES.  211 

These  two  retorts  are  placed  in  a  specially  constructed  furnace. 
First  the  upper  retort  is  heated  to  bright  redness,  and  then  the 
lower  retort  is  so  heated  as  to  bring  the  mass  to  a  state  of 
fusion. 

In  BrunquelPs  second  improvement,  only  one  cylinder  is  used, 
the  lower  half  of  which  is  filled  with  the  ordinary  mixture  and  the 
upper  half  with  charcoal  and  potash.  This  cylinder  is  suspended 
by  a  chain  and  may  be  raised  or  lowered  at  will  into  a  vat-like  fur- 
nace which  is  provided  with  a  grate  containing  a  hole  through  which 
the  cylinder  may  pass.  At  the  beginning  of  the  operation  the 
cylinder  is  lowered  deep  enough  so  that  only  the  upper  part  is  sub- 
jected to  the  heat;  when  this  part  has  reached  the  desired  tempera- 
ture, the  cylinder  is  raised  so  that  it  is  found  completely  in  the 
furnace  and  consequently  heated  on  all  sides. 

In  this  way,  in  the  first  as  well  as  in  the  second  apparatus,  the 
gases  set  free  by  the  mixture  of  the  lower  .part  passed  through  the 
upper  mixture.  Notwithstanding  these  advantages  Brunquell's  two 
processes  have  never  been  adopted  on  an  industrial  scale. 

Still  another  improvement,  due  to  Brunquell,  consists  in  con- 
verting most  of  the  nitrogen  into  volatile  products  by  means  of 
repeated  distillations  with  lime,  then  to  utilize  the  ammoniacal 
products  thus  obtained  for  the  manufacture  of  ferrocyanide  by 
passing  them  through  a  series  of  cylinders  filled  with  charcoal  and 
potash  heated  to  bright  redness.  The  ammonium  cyanide  thus 
formed  is  collected  in  a  strong  solution  of  sulphate  of  iron.  Cyanide 
of  iron  is  formed,  which  when  boiled  with  potash  is  converted  into 
potassium  ferrocyanide.  For  a  certain  time  this  process  was  tried 
in  France,  with  this  modification,  however,  that  the  ammonium 
cyanide  was  absorbed  by  a  strong  solution  of  potash  to  which  a 
salt  of  iron  had  been  added. 

Karmrodt's  Process. — Along  the  same  line,  Karmrodt's  process 
should  also  be  mentioned.  The  object  of  this  process  is  the  same 
as  that  of  Brunquell,  and  it  may  profitably  be  combined  with  the 
manufacture  of  animal  black.  The  apparatus  used  consists  of 
two  parts,  the  carbonization  vessel  and  a  cylinder  charged  with 
wood  charcoal  impregnated  with  potash.  The  two  parts  are  con- 
nected by  means  of  a  tube.  The  cylinder,  which  is  vertical,  is  pro- 
vided with  a  fire-grate;  one  begins  heating  the  cylinder  by  means 


212      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

of  this  fire-grate.  With  the  aid  of  a  special  appliance  the  prod- 
ucts of  combustion  are  conducted  either  into  the  main  chimney 
or  into  a  flue  joined  to  the  carbonizing  retort.  When  the  cylinder 
has  reached  the  temperature  of  redness,  the  gases  of  the  fire-grate 
are  conducted  under  the  carbonizing  retort.  The  volatile  prod- 
ucts here  liberated  pass  through  the  connecting  tube  into  and 
through  the  cylinder. 

The  yield  is  appreciably  greater  than  by  the  ordinary  process, 
but  it  is,  nevertheless,  far  from  the  theoretical  yield,  which  the 
whole  of  the  ammoniacal  products  set  free  should  give. 

Several  processes  for  the  conversion  of  sulpho cyanides  into 
ferrocyanides  have  been  invented,  among  which  only  two  deserve 
to  be  taken  into  consideration. 

Conroy's  Process. — The  first  is  that  of  Conroy,  Hurter,  and 
Brock  (1896).  It  consists  in  treating  the  crude  sulphocyanide 
with  a  solution  of  ferric  or  ferrous  chloride.  The  mixture  is  heated 
to  270-280°,  in  an  autoclave  provided  with  a  stirrer,  in  the  pres- 
ence of  an  excess  of  iron,  preferably  reduced  iron. 

The  sulphocyanide  is  converted  into  a  mixture  of  ferrocyanide 
and  sulphide  of  iron,  which  is  collected,  washed,  and  finally  decom- 
posed with  a  caustic  alkali.  The  residue  from  the  treatment  with 
alkali,  consisting  of  a  mixture  of  sulphide  of  iron  and  ferric  and 
ferrous  hydrate,  is  treated  with  hydrochloric  acid,  which  forms  iron 
chloride,  which  may  be  used  anew.  The  hydrogen  sulphide  thus 
liberated  is  collected  and  used. 

Musspratt's  Process. — The  second  process  is  that  of  H.  E.  Hether- 
ington  and  E.  K  Musspratt  (English  patent  No.  5830,  March  20, 
1894). 

It  consists  in  treating  a  sulphocyanide  of  an  alkali  or  alkaline 
earth  with  metallic  iron.  First  finely  divided  iron  (filings,  turn- 
ings, or  iron  sponge)  is  heated  with  tar,  the  object  being  to  reduce 
the  oxid  which  always  forms  on  the  surface  of  these  products.  The 
iron  thus  prepared  is  mixed  with  sulphocyanide  and  tar  in  the  follow- 
ing proportions: 

Reduced  iron 70-80  parts 

Tar 20-40    " 

Sulphocyanide  of  potassium  or  sodium 100   " 


MANUFACTURE  OF  FERROCYANIDES.  213 

This  mixture  is  heated  to  350°  F.  in  a  closed  vessel  connected 
by  a  tube  to  a  condensation  retort.  This  retort  serves  in  condens- 
ing the  sulphocyanide  which  might  be  volatilized  during  the  opera- 
tion. 

The  product  of  the  reaction  consists  of  a  mixture  of  alkali  ferro- 
cyanide,  iron  and  alkali  sulphides,  and  tarry  residue.  It  is  treated 
with  hot  water,  the  solution  thus  obtained  being  treated  with  car- 
bonic acid,  which  removes  the  hydrogen  sulphide,  and  then 
concentrated  to  crystallization.  In  case  of  ferrocyanide  of  sodium, 
it  is  best  to  concentrate  directly. 

Goerlich  and  Wichmann's  Process. — This  process  (German  pat- 
ent No.  9139,  Aug.  4,  1894,  March  11,  1895)  is  practically  the  same. 

It  consists  in  fusing  alkali  sulphocyanide  with  iron  and  treating 
the  product  of  fusion,  before  lixiviation,  with  a  current  of  moist  air 
mixed  with  carbonic  acid.  In  this  way  ferrocyanide,  sulphur, 
alkali  sulphide,  and  carbonate  are  obtained: 

2[K6(CN)6-6FeS]+170  +  21H20+2C02 

=2K4Fe(CN)6.3H20+2C03K2+5Fe2(OH)64-12S. 

By  this  process  almost  the  whole  of  the  sulphur  is  removed,  and 
alkali  carbonate  is  obtained  instead  of  alkali  sulphide. 

In  the  absence  of  carbonic  acid,  the  reaction  is  as  follows : 

2K6(CN)6  -  6FeS  + 150+ 21H20 

=2K4Fe(CN)6  -3H20+ 2K2S +5Fe2(OH)6 +10S. 

The  oxidized  product  is  treated  with  water,  and  the  soluble  salts  are 
separated  by  fractional  crystallization.  The  residue  may  be  used 
in  recovering  metallic  iron. 

Process  of  the  Works  du  Castelet. — Lastly,  we  will  mention  the 
extremely  original  process  described  in  the  patent  No.  308808  of 
March  8,  1901,  taken  by  La  Societe  des  Usines  du  Castelet,  and 
Leriche. 

It  consists  in  causing  a  gaseous  mixture  of  J  acetylene  and  f 
ammonia  to  act,  at  a  nascent  red  heat,  upon  an  intimate  mixture 


214       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

of  oxid,  carbonate,  or  hydrate  of  iron  and  alkali  oxid  in  a  closed 
vessel.     The  reaction  is  as  follows: 

6C2H2  +  12NH3  +  8KOH + Fe203 = 2Fe(CN)  6K4  +  HH20 + 34H. 

The  product  is  dissolved  in  boiling  water,  the  clear  solution  being 
decanted,  evaporated,  and  allowed  to  crystallize  on  cooling. 

II.  EXTRACTION  OF  CYANIDE  COMPOUNDS  FROM  ILLUMINAT- 
ING-GAS AND  FROM  THE  BYPRODUCTS  OF  ITS  MANU- 
FACTURE. 

The  manufacture  of  illuminating-gas  has  made  great  strides  in 
the  last  thirty  years  in  England,  Germany,  and  in  France.  Thus 
the  annual  consumption  of  gas  in  England  reaches  almost  3000 
million  cubic  meters;  in  France  it  is  about  700  million  cubic 
meters. 

As  will  be  seen  later,  the  cyanide  compounds  exist  already  formed 
in  the  gas.  It  is  therefore  quite  natural  that  one  should  think  of 
reaping  some  advantage  from  it.  To  be  sure,  the  percentage  is 
quite  small,  and  sometimes  even  trifling;  but  on  the  other  hand, 
if  one  thinks  of  the  enormous  quantity  of  gas  annually  produced 
in  the  different  countries,  one  can  easily  conceive  how  the  gas 
industry  may  offer  a  profitable  source  of  cyanide  production. 

Further,  it  should  be  stated  that  cyanogen  is  an  injurious  product 
which  it  is  necessary  to  remove  before  delivering  the  gas  for  con- 
sumption. It  decreases  the  illuminating  power  perceptibly,  and 
is  a  toxic  product.  Besides  its  being  absolutely  necessary  to  remove 
it  from  the  gas,  there  is  profit  in  its  recovery. 

In  England  the  question  of  cyanides  in  the  manufacture  of  gas 
has  keenly  prejudiced  the  mind,  and  the  manufacturers  and  investi- 
gators have  foreseen  the  advantage  to  be  derived  in  these  sub- 
stances in  a  country  so  rich  in  coal  and  gas.  Germany  is  not  at  all 
behind  in  this  respect,  there  being  few  gas-works  which  do  not  recover 
the  cyanide  compounds. 

On  the  other  hand,  France  has  shown  but  little  interest  in  this 
question,  and  even  at  the  present  time  there  seems  little  disposi- 
tion to  extend  this  industry. 


MANUFACTURE  OF  FERROCYANIDES.  215 

Moreover,  it  is  a  fact  to  be  regretted  that  in  France  so  little 
importance,  and  sometimes  even  not  any  at  all,  is  attached  to  the 
by-products  of  certain  manufactures.  It  is  not  a  rare  sight,  indeed, 
to  see  numerous  works  neglecting  such  an  interesting  and  often 
remunerative  question  as  the  recovery  of  by-products.  Thus,  for 
example,  in  the  case  of  illuminating-gas,  there  are  to  our  knowledge 
works  of  importance  which  do  not  even  condescend  to  take  the 
trouble  to  purify  the  gas,  or  if  they  are  compelled  to  do  this  because 
of  hygienic  statutes,  do  not  get  any  profit  out  of  their  sluice  waters 
or  from  their  spent  oxid. 

And  yet  in  most  cases  the  recovery  and  utilization  of  by-prod- 
ucts (especially  in  the  industry  which  we  are  discussing)  require 
but  slight  costs  of  installation,  costs  which  are  repaid  by  the  profits 
obtained  and  by  a  better  quality  of  product,  which  is  the  chief  ob- 
ject of  the  manufacturer.  It  should  also  be  stated  that  the  process 
of  recovering  these  by-products  does  not  generally  modify  the 
carrying  on  of  the  operations. 

Thus,  if  one  considers  that  in  France  the  manufacture  of  illu- 
minating-gas requires  annually  about  4,000,000  tons  of  coal,  and 
that  from  each  ton  one  can  extract  cyanide  compounds  worth  2-3 
francs,  it  is  easily  seen  that  the  illuminating-gas  industry  could 
recover,  each  year,  a  profit  of  8  to  12  million  francs,  which  is  not 
at  all  an  amount  to  be  neglected. 

One  objection  may  be  interposed  to  the  above  remarks,  and  that 
is,  that  in  France  many  gas-works  are  of  but  slight  importance, 
and  under  the  circumstances  the  recovery  of  these  by-products 
seems  to  offer  no  benefit  considering  the  small  amount  of  product  to 
be  treated.  To  this  objection  the  following  reply  may  be  made: 
Most  of  the  gas-works  are  in  the  hands  of  powerful  companies  often 
possessing  a  large  number  of  works.  It  would  be  a  simple  matter 
for  each  works  to  recover  the  cyanide  compounds,  and  to  obtain 
concentrated  products  (e.g.,  masses  rich  in  cyanide)  which  might 
be  profitably  transported  to  a  central  works,  which  could  be  espe- 
cially occupied  with  the  treatment  of  by-products  furnished  by  all 
the  works  of  the  company.  The  expense  would  be  slight  and  large 
profits  would  be  assured. 

From  all  the  foregoing  remarks  it  follows  that  the  gas  industry 
may  with  advantage  prove  a  source  of  production  of  cyanide  com- 


216       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

pounds,  a  production  which  would  require  but  little  expense  if  it 
were  well  understood,  and  which  under  these  conditions  would 
almost  suffice  for  the  demand  in  the  cyanides. 

There  is  therefore,  every  reason,  and  it  is  also  necessary,  that  the 
cyanide  compounds  should  be  recovered  from  the  gas,  and  one  should 
encourage  every  gas-manufacturer  so  to  do. 

We  shall  now  study  the  various  ways  proposed  to  bring  about 
this  operation  profitably,  but  before  that  it  seems  necessary  to 
mention  briefly  in  what  the  manufacture  of  illuminating-gas  con- 
sists. 

As  is  well  known,  illuminating-gas  is  a  product  of  the  distilla- 
tion of  coal  in  closed  vessels.  Coal  used  in  the  manufacture  of 
gas  is  the  dry  smiths'  coal  burning  with  a  long  flame,  and  contain- 
ing the  following  percentage  composition  (water  and  ash  free) : 


100.00 

The  principal  types  of  coal  most  commonly  used  are  those 
from  Nord,  Pas-de-Calais,  Mons,  the  Sarre,  Ruhr,  and  New- 
castle. This  distillation  takes  place  in  retorts,  formerly  made 
of  cast  iron,  but  now  of  refractory  brick,  arranged  ordinarily 
in  a  series  of  seven  or  nine,  in  a  furnace  which  is  heated  either 
•directly  with  coke  or  by  means  of  combustible  gases  produced 
"by  a  gas-generator  placed  under  the  furnace  for  the  recovery  of 
the  heat.  These  retorts,  whose  dimensions  vary  with  the  size  of 
the  works,  are  heated  to  a  temperature  of  about  1100°.  The  result- 
ing gas  consists  of  a  very  complex  mixture  of  different  products 
(volatile  and  non-volatile  hydrocarbons,  ammonia,  and  ammoniacal 
•salts,  hydrosulphuric  and  hydrocyanic  acids).  Thus  obtained,  this 
product  is  unfit  for  domestic  use,  and  must  therefore  be  subjected 
to  purification.  The  object  of  this  purification  is  to  separate  the 
products,  which  on  account  of  their  easy  condensation  would  befoul 


MANUFACTURE  OF  FERROCYANIDES.          217 

and  obstruct  the  pipes,  or  which  on  account  of  their  own  character- 
istics would  considerably  decrease  the  illuminating  power  of  the 
gas,  or  would  constitute  a  source  of  danger  to  the  health  of  the 
consumers  on  account  of  their  noxious  properties. 

The  purification  of  gas  is  carried  on  in  two  stages:  the  first 
is  purely  physical,  whereas  the  second  is  based  on  chemical 
reactions. 

The  physical  purification  consists  in  removing  all  the  easily 
liquefiable  or  condensable  products;  the  chemical  purification 
consists  in  absorbing  all  the  harmful  substances  which  escape  the 
physical  by  means  of  certain  definite  substances.  The  method 
of  procedure  is  as  follows: 

On  emerging  from  the  retorts  the  gas  passes  into  a  horizontal 
cylindrical  apparatus  half  filled  with  water  into  which  cylinder 
outlet  tubes. from  all  the  retorts  converge.  The  level  of  the  water 
is  kept  constant  by  means  of  an  overflow.  The  gas  abandons  in 
this  apparatus  the  less  volatile  products  (tars)  and  a  portion  of 
the  ammonia.  From  there  the  gas  goes  to  a  collector,  a  very  long 
horizontal  tube  about  0.80  metre  in  diameter,  where  a  great  part 
of  the  light  tars  that  have  escaped  the  previous  treatment  are 
deposited.  Then  it  goes  into  a  condenser  or  cooler  consisting  of 
a  system  of  inverted  U  tubes,  joined  to  a  rectangular  box,  divided 
into  sections  by  partitions,  into  which  the  condensed  products 
are  collected  (water-vapor,  ammoniacal  salts,  ammonia,  and  the 
tars  which  have  escaped  the  first  and  second  treatment)..  The  last 
traces  of  these  products  are  removed  in  the  scrubber,  a  tall  cast- 
iron  cylinder  consisting  of  two  chambers  filled  with  coke  and  into 
which  a  thin  stream  of  water  flows  in  a  direction  opposite  to  that 
of  the  incoming  gas.  Finally  by  passing  the  gas  through  the 
Pelouze  and  Audouin  condenser  the  last  traces  of  tar  are  removed,, 
and  it  only  remains  to  subject  the  gas  to  the  second  stage  for 
chemical  purification.  For  this  purpose  the  gas  passes  into  a 
series  of  boxes  filled  with  a  mixture  of  sawdust,  ferric  oxid,  lime, 
and  sulphate  of  lime,  which  absorbs  the  ammonia,  carbonic, 
hydrosulphuric,  hydrocyanic,  sulphocyanic  acids,  etc.  When  this 
mixture  no  longer  exerts  any  purifying  action,  it  is  "  revivified  " 
by  spreading  and  stirring  it  in  the  air,  when  it  may  be  used 
again. 


218       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 


As  may  be  seen  by  this  short  sketch  the  manufacture  of  gas 
yields  many  different  products  which  may  be  divided  as  follows: 


I.  COKE. 


II.  AMMONIACAL  LIQUORS. 


Principal 
elements 

Minor 
elements 


(  Ammonium  carbonate (NH4)8CO» 

( 


Gas 


Illuminating 
elements 


More  illuminating  ele- 
ments 


Elements  which  affect 
the  purity  of  the  gas 


Ammonium  sulphide 

r  Ammonium  chlorid NH4C1 

<  Ammonium  cyanide NH4CN 

(  Ammonium  sulphocyanide NH4CNS 

III.  ILLUMINATING-GAS. 

i 

Acetylene C2H2 

Ethylene C2H4 

Propylene C^H6 

Butylene C4H8 

Allylene C3H4 

Crotonylene C4H6 

Terrene C6H8 

Benzol C6H6 

Thiophene C4H4S 

Styrolene C8H8 

Naphthalene Ci0H8 

Methylnaphthalene CnHi0 

Acetylnaphthalene C,2Hi0 

Fluorene CuH10 

Fluoranthane Ci5Hi0 

Propyl C3H7 

Butyl C4Htt 

f  Hydrogen H2 

|  Methane CH4 

I  Carbon  monoxid CO 

Carbonic  acid CO2 

Ammonia NH8 

Cyanogen CN 

Sulphocyanogen CNS 

Methylcyanide C2H3N 

Hydrogen  sulphide H,S 

Sulphide  of  carbon CS2 

Sulphides  of  the  hydrocarbons — 

Oxysulphide  of  carbon COS 

Nitrogen N 


Vapors 


IV.  TAR 


MANUFACTURE  OF  FERROCYANIDES.          21  & 

V.  PURIFYING  MATERIALS. 

Varying  in  composition  according  to  the  nature  of  the  mixture  used,  but 
generally  containing: 

Sulphate  of  ammonia, 
Ferrocyanide  of  ammonia, 
Sulpho  cyanide  of  ammonia , 
Cyanide  of  ammonia, 
Prussian  blue, 
Sulphide  of  iron, 
Sulphur, 
Oxid  of  iron, 
Sawdust,  tar,  etc. 

The  amounts  vary  according  to  the  kind  of  coal  used,  but,  as 
a  rule,  from  100  klgm.  of  coal  the  following  are  obtained: 

I.  Coke 70  klgm.  =1.8  hectoliters 

II.  Gas 30  cu.  m.  D  =  0.4 

III.  Tar.  '. 3J  to  6  klgm.  D  =  1.2 

IV.  Ammoniacal  liquors 6-9  klgm.  1  to  8°  Baume 

(corresponding  to  1-5%  pure  ammonia) 

Of  these  various  products  three  only  are  of  interest,  because 
they  contain  cyanide  compounds,  namely: 

1.  Gas  itself. 

2.  Ammoniacal  liquors. 

3.  Purifying  materials. 

We  shall  take  up  these  three  substances  one  after  the  other, 
in  order  to  extract  from  the  products  of  the  distillation  of  coal 
the  cyanide  derivatives  which  they  may  contain,  and  which  quite 
naturally  vary  according  to  the  nature  and  the  composition  of  the 
raw  material  used,  and  according  to  the  methods  of  conducting 
the  distillation. 

But  before  taking  up  the  extraction  of  cyanides  in  the  manu- 
facture of  gas  it  would  seem  indispensable  to  review  the  various 
theories  set  forth  concerning  the  formation  of  these  compounds 
and  the  reactions  which  may  produce  them. 

Cyanide  compounds  are  naturally  formed  in  the  production  of 
illuminating-gas,  and  they  may  be  found,  in  the  various  stages  of 
the  manufacture,  in  the  following  forms:  Cyanogen,  sulphocy- 


220       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 


anogen,  sulphocyanic  acid,  hydrocyanic  acid,  cyanide,  ferrocyanide, 
sulphocyanide  of  ammonium,  etc. 

The  nitrogen  necessary  for  the  formation  of  these  compounds 
comes  from  the  coal,  which,  according  to  the  character  of  the  coal 
used,  contains  various  amounts. 


%    Kind  of  Coal. 

Per  Cent  N. 

Analyst. 

FRENCH  COALS. 
Haut-fleau  ("fat  ")  

.15 

de  Marsilly 

Escouffiaux 

25 

Agrappe 

375 

Bracquignies  ("half  -fat") 

00 

Mariemont  ........ 

75 

Valenciennes  ("fat  ")     

65 

Bruay  

875 

it 

Noeux  

525 

tt 

Bully 

34 

LieVin                

57 

Bousquet  d'Orb 

40 

Sables  (washed)  

67 

Trelys         "        

96 

Tre"lys  (crude)  

63 



Martinet  (washed)  „ 

31 



Fontanes       '  '        

.67 



Givors  

.65 

Ch.  MSne" 

Rouchamp,  1.  . 

.09 

Scheurer-Kestner 

"           2 

06 

i  ( 

"           3                                   

00 

tt 

CHARLEROI  BASIN. 

Poirier  ("fat")  

1  375 

de  Marsillv 

Carabinier  (French) 

1  00 

it       y 

Bois  d'Heignes   

0  40 

it 

ENGLISH  COALS. 
Three-quarter  vein  

1  65 

Percy 

Beg  vein         

1  47 

(Lab'y  of  Mines,  London) 

Low    "             

2  05 

Wolverhampton  

1  84 

Doul  in  (South),  Wales  

1  28 

Newcastle  

1  32 

Glamorgan  

1  69 

Northumberland  

2  05 

Scheurer-Kestner 

1  1 

2  37 

Ch  Me"ne" 

South  of  Wales  coal  

1  65 

n      ii      t  (        it 

1  49 



Lancashire  (uninflammable)  

1  93 



Scotland                "               

2  09 



ft                     tt 

1  33 



1  1                     1  1 

1  57 



"        "speakcoal" 

1  20 

Cannel-coal-Wigan  (Lancashire) 

2  12 



'  '                 Tyneside  (Newcastle)  .  . 

1  85 

_ 

Anthracite  (South  Wales)          

0  83 



Boghead  

0  96 

Genny 

tt 

0.78 

Matter 

MANUFACTURE  OF  FERROCYANIDES. 


221 


Kind  of  Coal. 

Per  Cent  N. 

Analyst. 

GERMAN  COALS. 

0  50 

Scheurer-Kestner 

Alien  wald            '  ' 

0  50 

Hernitz                 "          

0.50 



Friedrichsthal     "                •  •  • 

0  50 

Louisenthal                         

0  50 

Konigshiitte  (Prussia)       

0  59 

Schwachhof  er 

Morgenstern         '  '             

0  41 

Hermenegilde  (Low  Silesia)  

0  18 

= 

Carolinen  (Prussia)      

0  24 

„  

Jaklowetz  (Low  Silesia)        ....          .          . 

0  20 

Waterloo  (Prussia) 

0  40 

Altendorf                             

1  00 

Scheurer-Kestner" 

Consolidation                     

1  50 

Boldon                         

1  45 

__ 

Bohemian                

1  87 

Zwickau           

1  20 

___ 

Saar       

1  06 

, 

From  the  foregoing  table,  the  average  content  of  nitrogen  in 
coal  may  be  seen  to  be  1  to  1.6%. 

The  distillation  of  coal  distributes  this  nitrogen  among  the  vari- 
ous products  formed,  and  only  a  small  proportion  passes  into  the 
state  of  cyanide  compounds. 

Forster  studied  the  migration  of  nitrogen  produced  during  the 
distillation    of    coal    in  closed   vessels    (Journal  of  Gas   Lighting, 
1882).     One  of  his  experiments  was  made  with  a  coal  containing 
1.73%  nitrogen;    and  this  he  found  distributed  as  follows: 
0.251  or  14.50%  passes  into  ammonia 
0.027  or    1.56%      "        "    cyanogen 

0.863  or  49.90%  remains  in  the  coke  [state 

0.589  or  34.04%  passes  into  the  tars,  and  into  the  gas  in  a  gaseous 
1.73        100.00 

Knublauch,  who  repeated  the  same  experiment  on  three  samples 
of  coal,  found: 


Total  nitrogen  of  the  coal 1 . 555 

Nitrogen  in  the  coke 0. 466 

Nitrogen  in  the  gas 0. 856 

Nitrogen  in  the  form  of  ammonia 0. 185 

Nitrogen  "    "      "     "  cyanogen 0.0268 

Nitrogen  in  the  tars 0.0212 


2. 

1.479 
0.526 
0.696 
0.208 
0.0278 
0.0212 


3. 

1.176 
0.751 
0.189 
0.187 
0.018 


1.555      1.479      1.17a 


•222       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

Or  for  for  every  100  parts  of  nitrogen  contained  in  the  coal,  there  are 

i.  2.  3. 

JSfitrogen  in  the  coke 30.0        35.6          63.9 

"   "     gas 55.0  47.1  21.1 

"   "    form  of  ammonia 11.9  14.1  11.6 

"        "    "      "     ll    cyanogen 1.8  1.8  1.8 

"    "    tar 1.3  1.4  1.3 

100.0      100.0        100.0 

Leybolt  (Journal  fur  Gasbeleuchtung,  1890)  gives  the  following 
results : 

Coke 31.    to  36.  % 

Ammonia 10.    to  14.  % 

Cyanogen 1.5to    2.   % 

Tar ,.     l.Oto    1.3% 

Gas 46 . 0  to  56 . 0% 

Guegen  (Journal  du  gaz  et  de  Pelectricite  1884)  likewise 
studied  the  distribution  of  the  nitrogen  in  the  products  of  the 
distillation  of  two  coals,  carried  on  at  900°  in  sandstone  retorts. 


Nitrogen  in  the  form  of  ammonia 

Nitrogen  in  the  form  of  cyanogen  in  the  tar  and  in 

the  gaseous  products 

Nitrogen  in  the  coke 


1. 

Coal  from  Grand- 

Buisson,  Mons, 

Belgium. 


2. 
Coal  from  Li6vin. 


Distribution  of  100  Parts  Nitrogen. 


34 

27 
39 


100 


19 

29 
52 


100 


These  figures  are  not  at  all  absolute:  they  vary  with  the  nature 
of  the  coal,  the  method  of  operation  in  the  works,  the  temperature 
of  the  distillation,  etc.,  yet  they  show  that  the  amount  of  cyanide 
compounds  formed  is  relatively  small,  and  that  it  can  only  become 
of  value  when  large  quantities  of  coal  are  treated. 


MANUFACTURE  OF  FERROCYANIDES.  223 

Cyanogen  is  therefore  always  formed  in  very  small  quantities 
in  the  distillation  of  coal.  The  amount  formed  depends  much  on  the 
temperature  of  the  distillation,  cyanogen  not  being  formed  except 
in  brisk  distillations  carried  on  at  a  high  temperature.  In  distilling 
coal  at  a  higher  temperature,  Foulis  of  Glasgow  found  that  2831 
liters  of  gas  yielded  6.5  grams  of  cyanogen,  while  when  working  at 
a  low  temperature  this  amount  was  cut  down  to  less  than  half.  Accord- 
ing to  Hunt,  the  most  favorable  temperature  is  950°  and  above, 
while  at  700  to  800°  one  would  obtain  only  one  twelfth  as  much 
cyanogen.  This  remark  is,  moreover,  confirmed  by  the  experi- 
mental fact  that  the  greatest  part  of  the  cyanogen  is  formed 
toward  the  end  of  the  distillation — that  is,  at  the  moment  when  the 
temperature  is  the  highest,  and  at  this  very  moment  the  quantity 
of  ammonia  formed  is  very  small. 

A  small  yield  of  cyanogen  therefore  accompanies  a  large  yield 
of  ammonia,  and  vice  versa. 

Perthuis  carried  out  a  series  of  experiments  which  show  this 
to  be  true,  and  that  the  yield  of  cyanogen  reaches  its  maximum  at 
the  end  of  the  distillation,  while  at  the  beginning  it  is  almost  nothing: 

Length  of  Hydrocyanic  Acid  Retained  by 

Distillation.  100  Cu.  M.  of  Gas. 

1-2  hours trace 

3-4     "      77.1  grams 

5-6     "      142.1      " 

The  form  in  which  the  cyanogen  comes  out  of  the  distillation 
retorts  has  given  rise  to  many  discussions,  and  the  opinions  ex- 
pressed relative  to  this  subject  vary  greatly. 

According  to  some  investigators,  cyanogen  occurs  in  the  gas  in 
the  form  of  cyanide  and  sulphocyanide  of  ammonium. 

The  reaction  would  be  that  indicated  by  Kuhlmann: 

C  +  2NH3=CN-NH4+H2. 

When  this  ammonium  cyanide  comes  in  contact  with  sulphur 
and  sulphide  of  carbon  in  the  highly  heated  retort  it  becomes  par- 
tially transformed  into  ammonium  sulphocyanide. 

But,  on  the  other  hand,  the  experiments  of  Bergmann  clearly 
prove  that  the  action  of  ammonia  on  carbon  or  on  carbon  monoxid 


224       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

at  a  red, heat  does  not  yield  ammonium  cyanide,  but  hydrocyanic 
acid,  according  to  the  reaction 

C+NH8»CNH+Ha. 

According  to  Lewis,  and  this  is  the  most  probable  opinion,  the 
cyanogen  found  in  gas  may  exist  therein  only  in  the  form  of  free 
cyanogen  or  free  hydrocyanic  acid.  Lewis  bases  his  views  upon  the 
following  principles:  (1)  It  is  impossible  that  cyanogen  should 
exist  in  the  gas  in  the  form  of  sulphocyanic  acid  (CNSH),  for  this 
latter  in  the  presence  of  hydrogen  becomes  decomposed  into  hydro- 
cyanic acid  and  hydrogen  sulphide: 

CNSH  +  2H  =  CNH+H2S. 

(2)  Neither  can  it  exist  under  the  form  of  ammonium  cyanidef 
since  this  salt  is  decomposed  from  the  time  the  temperature  exceeds 
26.6°  C. 

(3)  It  is  also  quite  improbable  that  it  occurs  therein  in  the  state 
of   ammonium  sulphocyanide,  experiments   having   clearly   proven 
this. 

Finally,  other  investigators  admit  that  ammonium  cyanide  is 
formed,  but  that  it  becomes  decomposed  by  carbonic  acid  con- 
tained in  the  gas,  this  decomposition  yielding  hydrocyanic  acid 
and  ammonium  carbonate.  This  would  of  course  explain  the 
absence  of  ammonium  cyanide  in  the  scrubbers. 

However  that  may  be  the  formation  of  cyanogen  compounds 
in  gas  takes  place  in  the  distillation  retorts  at  a  high  temperature; 
it  probably  results  from  the  action  of  ammonia  on  carbon  or  on 
carbon  monoxid  at  a  high  temperature.  This  reaction  in  all 
probability  causes  the  formation  of  free  hydrocyanic  acid,  which 
in  the  course  of  its  passage  through  the  series  of  apparatus  becomes 
transformed,  as  will  be  seen. 

In  the  ammoniacal  liquors,  cyanogen  is  found  principally  under 
two  forms:  as  ferrocyanide  and  sulphocyanide  of  ammonium. 
Ammonium  cyanide  exists  therein  but  rarely  and  in  a  subsidiary 
manner. 

According  to  Lewis,  ammonium  ferrocyanide  will  be  formed  by 
the  action  of  free  hydrocyanic  acid,  in  the  presence  of  ammonia. 


MANUFACTURE  OF  FERROCYANIDES.  225 

on  iron  sulphide,  which  is  itself  formed  by  the  action  of  hydrogen 
sulphide  on  the  iron  framework  of  the  condenser: 

6CNH  +  6NH3+FeS=Fe(CN)6(NH4)4+(NH4)2S. 

The  ammonium  ferrocyanide  cannot  in  any  way  come  from  the 
iron  contained  in  the  coal,  nor  be  formed  in  the  retorts  because 
all  the  ferrocyanides  are  decomposable  at  temperatures  much  lower 
than  those  reached  in  the  retorts. 

As  to  the  ammonium  sulphocyanide,  its  origin  is  a  little  more 
obscure  and  still  requires  some  elucidation. 

And  yet  Lewis  thinks,  from  experiments,  that  it  results  from 
the  action  of  carbon  bisulphide  on  ammonium  sulphide, 

(NH4)2S  +  CS2  =  2H2  +  CNS  •  NH4, 

this  sulphide  of  carbon  being  itself  produced  by  the  action  of  the 
sulphur  of  pyrites  contained  in  the  coal  on  the  carbon  at  the  tem- 
perature of  the  distillation. 

The  amount  of  ferrocyanide  and  of  sulphocyanide  of  ammonium 
found  in  ammoniacal  liquors  is  relatively  very  small.  Lewis  estimates 
that  on  an  average  181  grams  of  ferrocyanide  of  ammonium,  cal- 
culated as  Prussian  blue,  is  found  in  one  ton  of  coal,  and  of  sulpho- 
cyanide of  ammonium  he  found  226  to  907  grams  per  ton  of  distilled 
•coal. 

As  the  result  of  experiments  carried  on  in  certain  German  works 
— at  Wiesbaden,  Karlsruhe,  Mainz — Esop  gives  the  following 
figures  (Chemische  Industrie,  1892,  page  116). 

Ppr  PpTit  Ammonia  in  the 

Ammoniacal  Liquors. 

Sulphocyanic  acid 1 .22  18.05% 

"  1.51  19.03% 

"  "  2.33  36.05% 

Lunge  claims  that  the  quantity  of  sulphocyanide  of  ammonium 
contained  in  the  ammoniacal  liquors  in  the  manufacture  of  gas  in 
England  amounts  to  11  kilos  per  454  liters;  but  Clayfield  after 
numerous  experiments  was  able  to  find  but  0.453  kilo  per  454 
liters. 


226       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

« 

It  is  not  at  all  surprising  that  the  ferrocyanide  and  the  sulpho 
cyanide  of  ammonium,  both  very  soluble  in  water,  should  exist  in 
such  small  quantities  in  the  ammoniacal  liquors;  this  is  due  simply 
to  the  action  of  carbonic  acid  which  displaces  the  hydrocyanic  and 
the  sulpho  cyanic  acids  from  their  combinations. 

On  the  other  hand,  in  the  purifying  materials  the  cyanogen  is 
retained  almost  wholly,  and  if  we  consult  the  following  table  by 
Lewis,  it  will  easily  be  seen  that  immediately  after  passing  through 
the  first  purifier  the  quantity  of  cyanogen  compounds  contained 
in  the  gas  diminishes  considerably,  and  that  it  is  in  this  first  purifier 
that  the  greater  portion  of  the  cyanogen  products  formed  during  the 
manufacture  are  collected. 

Hydrocyanic  Acid 
per  Cubic  Meter. 

After  the  retorfs 19 . 2   to  30. 6     grams. 

"      "    condensers 18.9    to  29.0 

11      "    scrubbers 18.4    to  18.8 

"      "    1st  purifier 1.2    to  14.2 

"      "    2d        "       0.5   to    1.2 

"       "3d       "       0.45  to    0.50  gram. 

"       "4th      "       0.30to    0.40     " 

Leybold  had,  moreover,  made  similar  experiments,  showing  the 
progressive  elimination  of  cyanogen,  with  the  following  results: 

Hydrocyanic  Acid  Hydrocyanic  Acid, 

per  100  Cu.  M.  Per  Cent. 

I.  II.  I.  II.   ' 

Conduit 265.9  203.4  5.4          14.57 

After  condensation 251 . 6  173 . 6  45 . 09 

/'      1st  purifier 131.7 

'"     2d        "     83.3  59.5  18.2          56.15 

"     3d        "     61.6  8.16 

In  the  gasometer 41.2  19.8  15.5            9.73 

The  purifying  materials  are,  as  is  known,  composed  of  a  mixture 
.of  ferric  hydrate  and  sulphate  of  lime,  obtained  by  the  reaction  of 
Abime  on  sulphate  of  iron;  this  mixture  is  then  made  porous  with 
sawdust. 

The  gas,  on  coming  into  the  purifying  boxes,  contains  the  follow- 
ing impurities:  Hydrogen  sulphide,  ammonia  and  cyanogen  com- 


MANUFACTURE  OF  FERROCYANIDES.  227 

pounds.  Rather  complex  reactions  take  place  in  the  purifiers 
between  the  purifying  materials  and  the  impurities,  there  being 
formed  notably  ferrous  cyanide,  ferrocyanide  of  iron  and  ammonium,, 
carbonyl  ferrocyanide  of  sodium,  and  ammonium  sulphocyanide. 

The  formation  of  ferrocyanide  may  be  explained  in  various  ways. 

The  hydrocyanic  acid  would  react  on  oxid  of  iron  in  order  to 
form  ferrous  cyanide,  which  in  the  presence  of  oxygen  of  the  air 
would  become  converted  into  Prussian  blue : 

Fe203+4CNH  =  2Fe(CN)2+2H20+0, 

9Fe(CN)2  +  03  =  Fe203 + Fe7(CN)  18. 

It  follows,  however,  from  Leybold's  experiments  that  if  a  current 
of  hydrocyanic  acid  mixed  with  hyrdogen  be  passed  through  the 
purifying  materials  no  absorption  takes  place,  while,  on  the  other 
hand,  if  the  purifying  materials  be  first  saturated  with  hydrogen 
sulphide  the  hydrocyanic  acid  becomes  entirely  combined,  due  to 
the  previous  formation  of  iron  sulphide,  according  to  the  reaction 

FeS  +2CNH  =  H2S  +Fe(CN)  2, 

the  ferrous  cyanide  formed  then  becoming  converted  into  Prussian 
blue  under  the  action  of  atmospheric  oxygen. 

Other  investigators  claim  that  the  ferrous  cyanide  results  from 
the  action  of  ammonium  cyanide  on  oxid  or  sulphide  of  iron. 

FeO  +2CN  •  NH4  =  Fe(CN)2  +  (NH4)20 
or 

FeS + 2CN .  NH4  =  Fe(CN)  2  +  (NH4)2S, 

and  if  ammonium  cyanide  be  in  excess  there  is  formation  of  am- 
monium ferrocyanide: 

Fe(CN)2+4CN  -NH4  =Fe(CN)6  -  (NH4)4. 

In  every  case  it  is  to  be  noted  that  Prussian  blue  is  not  formed 
directly  in  the  purifiers,  but  by  oxidation  of  the  ferrocyanide. 
Moisture  or  the  use  of  steam  facilitates  the  formation  of  ferrocy- 
anides,  whereas  ammonia  prevents  it.  It  is  therefore  of  the  utmost 


228       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

importance,  if  one  wishes  to  obtain  materials  rich  in  ferrocyanide, 
to  wash  the  gas  as  completely  as  possible,  in  order  to  remove  the 
ammonia.  By  removing  the  ammonia  almost  entirely,  Knublauch 
succeeded  in  obtaining  materials  containing  up  to  24%  of  ferro- 
cyanide of  potassium  (reckoned  on  the  dry  matter). 

In  fact  ammonia,  oddly  enough,  facilitates  the  formation  of 
sulphocyanide  of  ammonium  or  of  sulphocyanide  of  iron.  Knublauch 
in  1877  was  the  first  to  show  the  close  relation  which  exists  between 
ammonia  and  sulphocyanogen,  and  he  showed  how  the  sulphocy- 
anides  may  be  formed  at  the  expense  of  ferrocyanides  if  the  washing 
of  the  gas  has  been  insufficient. 

Sulphocyanide  of  ammonium  exists  in  but  very  small  quantities 
in  gas  as  it  comes  to  the  purifying  boxes,  but  it  may  be  formed 
in  large  amounts  in  these  boxes,  especially  if  ammonia  or  ammonium 
sulphide  are  found  in  the  presence  of  finely  divided  sulphur  such 
as  exists  in  the  spent  oxids  or  in  the  presence  of  hydrogen  sulphide. 

According  to  Lewis  the  reactions  which  take  place  on  the  forma- 
tion of  sulphocyanide  are  as  follows: 

NH3  +  CNH  +  H2S  =  CNS  •  NH4  +  H2, 

Fe2S3  +  CNH  =  CNSH  +  2FeS; 
CNH  +  H2S  +  0  =  CNSH  -f  H20. 

Leybold  studied  this  phenomenon  and  analyzed  two  purifying 
masses  saturated  with  hydrogen  sulphide  which  had  been  sub- 
jected to  the  action  of  a  mixture  (1)  of  hydrocyanic  acid  and  am- 
monia and  (2)  hydrocyanic  acid  and  ammonium  sulphide: 

I.  II. 

CNH  +  NH3.  CNH  +  (NH4)2S. 

Water 23.60%  33.02% 

Sulphur . .... 24.98%  11.39% 

Prussian  blue 1 .70%  5.38% 

Ammonium  sulphocyanide 3 . 03%  4 . 40% 

Ammonia 2.05%  0.75% 

It  results  from  these  analyses  that,  in  the  case  of  ammonia, 
the  amount  of  sulphocyanide  formed  is,  as  is  known,  greater  than 
that  of  Prussian  blue,  and  that  in  the  case  of  ammonium  sulphide 
it  is  about  equal. 


MANUFACTURE  OF  FERROCYANIDES.  229 

The  presence  of  an  alkali  in  the  purifying  materials  is  likewise 
very  favorable  to  the  formation  of  the  sulphocyanides. 

During  the  "revivification"  of  these  materials,  if  care  be  not 
taken  to  avoid  heating,  the  formation  of  sulphocyanides  at  the 
expense  of  ferrocyanides  is  considerable.  Burschell  estimates  that 
it  may  sometimes  amount  to  30%  of  the  weight  of  ferrocyanides. 
This  transformation  is  due  to  the  action  of  ammonia  and  of  hydrogen 
sulphide  found  in  the  purifying  materials,  and  to  the  moisture  con- 
tained therein,  and  likewise  to  the  action  of  sulphur  and  the  alkali 
sulphides  on  the  ferrocyanides. 

As  may  be  seen  from  this  rapid  review  of  the  complicated  reac- 
tions which  control  the  formation  of  cyanogen  compounds  in  the 
gas  itself,  in  the  ammoniacal  liquors  and  in  the  purifying  materials, 
this  formation  is  intimately  dependent  upon  numerous  conditions. 
The  gas-worker  who  is  desirous  of  recovering  the  cyanogen  should 
strive  to  avoid  or  to  produce  them  according  as  they  are  injurious 
or  favorable. 

We  shall  now  take  up  the  various  processes  which  the  manu- 
facturer may  put  into  operation  in  order  to  extract  the  cyanide 
compounds. 

A.  In  the  illuminating-gas. 

B.  In  the  ammoniacal  liquors. 

C.  In  the  spent  oxid. 

A.    DIRECT   EXTRACTION  FROM   GAS. 

Although  the  presence  of  cyanogen  compounds  in  gas  has  been 
known  for  a  long  time  (it  is  mentioned  in  an  English  patent  in  1850), 
it  is  only  within  the  last  few  years,  on  account  of  its  limited  use 
in  the  arts,  that  any  attempt  has  been  made  to  derive  any  benefit 
from  it.  The  spent  purifying  materials,  or  Laming's  mixture,  were 
considered  as  valueless  waste  products,  and  it  was  not  till  1880 
that  a  French  manufacturer,  Gauthier-Bouchard,  thought  of  utiliz- 
ing them  for  the  manufacture  of  Prussian  blue  and  of  potassium 
ferrocyanide.  As  these  cyanogen  compounds  are  formed  naturally 
in  these  materials,  and  without  care  or  thought  on  the  part  of  the 
manufacturer,  this  process  has  been  but  little  improved.  But  from 
the  time  that  cyanides  became  useful  in  the  treatment  of  aurifer- 


230       METHODS  OP  MANUFACTURING  CYANIDE  COMPOUNDS. 

ous  minerals,  many  investigators,  especially  in  Germany,  perceived 
the  possibility  of  making  gas  a  profitable  source  of  cyanide  pro- 
duction, and  sought  to  extract  from  gas  the  greatest  amount  of 
cyanide  possible.  They  soon  recognized  that  Laming's  mixture, 
or  other  similar  materials,  were  but  an  imperfect  and  expensive 
source  of  production.  In  fact  it  is  easily  understood  that  this 
treatment  in  the  dry  way  has  the  disadvantage,  notwithstanding 
the  porosity  which  sawdust  gives  to  the  mixture,  of  presenting 
but  a  small  contact  action  to  the  cyanogen  and  its  compounds, 
and  that  the  absorption  of  these  bodies  is  necessarily  incomplete. 
Moreover  it  has  already  been  noticed  that  on  account  of  secondary 
reactions  appreciable  amounts  of  sulphocyanides  may  be  formed 
in  the  materials,  which  are  of  less  value  than  are  the  ferrocyanides, 
and  their  subsequent  conversion  into  cyanides  is  more  difficult. 

These  are  the  reasons  which  caused  the  investigators  to  seek 
the  extraction  of  the  cyanogen  compounds  as  completely  as  possible 
directly  from  gas.  At  present  these  processes  seem  to  prevail 
among  gas  manufacturers  who  are  anxious  to  derive  some  benefit 
from  such  an  important  by-product,  while  in  the  works  which, 
for  some  groundless  reason,  persist  in  refusing  to  consider  the  impor- 
tance of  cyanides  in  gas,  the  purifying  materials  are  still  being  worked 
for  the  Prussian  blue,  in  order  to  make  of  it  a  better  commercial 
product. 

In  other  works,  and  they  are  numerous  enough,  they  do  not 
even  try  to  obtain  materials  rich  in  f errocyanides ;  and  when  these 
materials  are  spent,  i.e.  do  not  absorb  any  more  hydrogen  sulphide, 
they  are  sold  to  manufacturers  of  Prussian  blue  or  of  cyanides. 

In  Germany  and  England  processes  for  direct  extraction  of 
cyanides  from  gas  are  established  on  a  large  scale,  and  it  is  to  be 
hoped  that  the  French  will  not  long  remain  behind  their  neighbors. 

The  ideal  method  of  direct  extraction  of  cyanide  compounds 
from  illuminating-gas  as  it  comes  from  the  retorts  would  be  to 
pass  it  through  an  alkaline  solution,  thus  forming  an  alkali  cyanide 
But  this  is  quite  impossible  on  account  of  the  presence  in  gas  of 
other  acid  gases,  e.g.  carbonic  acid  and  sulphuric  acid  which  could 
immediately  displace  hydrocyanic  acid  and  therefore  prevent  all 
formation  of  cyanide.  Therefore  the  idea  of  obtaining  cyanides 
directly  from  gas  must  be  abandoned. 


MANUFACTURE  OF  FERROCYANIDES.  231 

Combinations  upon  which  carbonic  acid  and  hydrogen  sulphide 
have  no  action  must  be  sought. 

Knublauch  Js  Process.. — Knublauch  was  the  first  investigator  to 
become  interested  in  this  important  question.  Knublauch,  who 
since  1877  had  undertaken  a  whole  series  of  researches  on  cyanogen 
in  illuminating-gas  was  led  during  his  experiments  to  find  a  method 
which  allowed  direct  extraction  of  the  cyanogen  products  from  gas 
in  a  wet  way  (German  patent  No.  41930,  Aug.  18,  1886  ;  French 
patent  No.  209770,  Nov.  25,  1890). 

This  process  consists  in  passing  the  gas  into  purifiers,  washers,  or 
scrubbers  containing  in  solution  one  or  more  of  the  substances  men- 
tioned in  the  two  following  groups:  (1)  alkalis,  ammonia,  ammoni- 
acal  liquors,  alkaline  earths,  magnesia,  carbonates  and  sulphites  of" 
these  bases ;  (2)  iron,  manganese,  zinc,  oxids,  hydrates,  or  carbon-- 
ates  (natural  or  artificial)  of  these  metals. 

Knublauch  noticed  that  carbonic  acid  and  sulphhydric  acid  did' 
not  in  any  way  interfere,  and  that  even  when  these  two  gases  were 
found  in  large  quantity  in  the  gaseous  mixture,  at  the  moment  of 
passing  through  a  solution  containing  both  iron  and  an  alkali, 
cyanogen  forms  with  them  ferrocyanide  with  so  great  an  energy 
that  the  affinity  of  carbonic  acid  and  hydrogen  sulphide  toward 
cyanogen  is  so  weakened  as  to  render  the  amount  of  hydrogen  sul- 
phide absorbed  insignificant. 

The  gas  should  always  pass  through  a  liquid  and  not  a  solid  mass,, 
and  this  liquid  should  be  agitated  during  the  passage  of  the  gas, 
which  passes  through  successively  a  series  of  absorption  apparatus 
so  arranged  as  to  permit  easy  change  of  the  order  of  succession. 

If,  for  example,  a  gas,  such  as  illuminating-gas,  containing,  besides 
cyanogen,  carbonic  acid  and  hydrogen  sulphide  be  passed  into  a 
solution  containing  a  ferrous  salt  and  an  alkali,  the  precipitated 
ferrous  hydrate,  Fe(OH)2  disappears  almost  wholly  in  the  state  of 
soluble  alkali  ferrocyanide,  while  only  a  small  portion  remains  in. 
suspension  in  the  liquid  in  the  form  of  sulphide  of  iron.  If  an  amount 
of  iron  greater  than  that  of  alkali  be  used,  an  insoluble  cyanide  is 
formed. 

The  amount  of  absorbent  material  to  be  used  for  a  definite  weight 
of  cyanogen  depends  on  the  nature  of  these  materials,  and  the 
proportions  naturally  vary  as  one  uses  mono  or  bivalent  bases, 


232        METHODS   OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

hydrates  or  carbonates,  natural  or  artificial  products.  In  general, 
for  every  molecule  of  hydrocyanic  acid,  a  molecule  of  alkali,  of 
alkaline  earth,  hydrate  or  carbonate,  and  somewhat  less  than  a 
molecule  of  iron  compounds  should  be  used.  The  quantity  of 
liquid  used  should  at  least  be  sufficient  to  allow  the  gas  to  bubble 
through. 

Knublauch's  method  has  received  but  few  trials  in  England. 
Its  want  of  success  was  due  not  to  the  results  which  it  yielded  but 
to  the  lack  of  interest  shown  by  the  manufacturers,  at  the  time  of 
its  appearance,  for  the  direct  recovery  of  cyanogen. 

Gasch's  Process. — The  process  of  Robert  Gasch  of  Mainz  (patent 
No.  201377,  Dec.  24,  1889)  consists  in  using  recently  precipitated  me- 
tallic sulphides,  which  with  the  cyanogen  of  the  gas  form  a  ferrocya^ 
'nide.  The  indispensable  condition  is  the  presence  of  ammonia,  which 
condition  is  found  in  illuminating-gas.  The  higher  the  temperature 
the  more  rapid  and  complete  is  the  conversion.  It  is  instantaneous 
at  from  50  to  60°.  The  action  of  the  heat  may  be  suppressed  when 
the  reaction  is  well  begun,  and  this  can  be  done  by  adding  a  cyanide 
precipitate  obtained  from  a  cyanide  solution  coming  from  a  previous 
operation.  The  operation  is  carried  on  by  means  of  ordinary 
washers,  or  by  the  means  of  vertical  boilers,  which  allow  intimate 
contact  of  the  gas  with  the  absorbent  materials,  and  this  apparatus 
is  so  placed  that  the  gas  which  passes  through  it  has  a  temperature 
not  exceeding  36°,  a  temperature  at  which  sulphocyanides  begin 
to  be  formed. 

According  to  the  author  of  this  process,  its  advantages  are  as 
follows : 

(1)  An  increased  yield  in  ammonium  ferrocyanide. 

(2)  High  concentration  and  purity  of  the  cyanide  liquors  under 
a  form  suitable  for  further  treatment. 

(3)  The  only  impurities  are  a-  small  amount  of  ammonium  and 
potassium  sulphides. 

Gasch  recommends,  moreover,  the  use  of  liquids  holding  in  sus- 
pension a  metallic  sulphide  such  as  iron  sulphide,  to  which  is  added 
a  milk  of  lime,  and  having  in  solution  a  soluble  salt  (oxalate  or 
sulphate  of  alkali,  an  ammonia  salt,  sulphate  of  magnesia,  aluminum, 
iron,  etc.). 

If,  for  example,  a  solution  of  sodium  sulphate  be  used  to  which 


MANUFACTURE  OF  FERROCYANIDES.  233 

is  added  a  milk  of  lime  and  having  in  suspension  sulphide  of  iron, 
a  weak  solution  of  sodium  ferrocyanide  will  be  obtained  contain- 
ing more  or  less  sodium  sulphide  and  a  deposit  of  sulphate  of 
lime  and  sulphide  of  calcium,  both  insoluble. 

Rowland's  Process. — This  process  (French  patent  No.  218215r 
March  21,  1892)  consists  essentially  in  having  the  ammoniacal 
liquors  of  the  scrubber  absorb  the  whole  or  greater  part  of  the  cyano- 
gen. For  this  purpose  Rowland  adds  an  iron  salt  to  the  water 
of  the  scrubber  in  suitable  quantity,  but  not  in  such  quantity  that 
iron  sulphide  will  be  formed.  The  optimum  amount  is  5.5%. 
Ammonium  ferrocyanide  is  formed  which  remains  in  solution.  After 
the  addition  of  a  fresh  quantity  of  salt  or  oxid  of  iron,  the  ammo- 
niacal liquors  are  distilled,  the  addition  of  iron  converting  the  ammo- 
nium ferrocyanide  into  double  ferrocyanide  of  iron  and  ammo- 
nium, which  is  insoluble  and  may  be  separated  from  the  liquor 
by  adding  milk  of  lime  and  filtering.  The  filtered  solution  is  heated 
to  boiling  and  sulphate  or  chloride  of  potassium  is  added,  thus  form- 
ing a  double  ferrocyanide  of  potassium  and  lime.  The  same  result 
may  be  obtained  by  acidifying  the  liquor  and  boiling.  The  double 
ferrocyanide  of  potassium  and  lime  is  treated  with  potassium  car- 
bonate, which  on  ignition  converts  it  into  alkali  ferrocyanide  and 
carbonate  of  lime.  A  strong  solution  is  made  and  allowed  to  crys- 
tallize. 

Fowlis'  Process. — Fowlis  of  Glasgow  has  patented  a  process 
(English  patent  No.  9474,  May  18,  1892)  which  is  similar.  The  gas, 
previously  freed  of  ammonia,  is  passed  through  a  solution  of  potas- 
sium or  sodium  carbonate  containing  oxid  of  iron  (Fe20s)  or  car- 
bonate of  iron  in  suspension.  This  solution  is  prepared  as  follows: 
To  25  liters  of  a  solution  of  ferrous  chloride  (FeCb),  containing 
150  grams  Fe  per  liter,  is  added  a  solution  of  7.5  kg.  carbonate  of 
sodium  at  98°  in  150  liters  water.  Carbonate  of  iron  is  precipitated, 
the  solution  of  sodium  chloride  is  decanted,  and  the  carbonate  of 
iron  is  put  in  suspension  in  a  solution  of  13.5  kg.  of  carbonate  of 
sodium  in  200  liters  of  water.  The  13.5  kg.  of  carbonate  of  sodium 
may  be  replaced  by  17.5  kg.  carbonate  of  potassium.  A  scrubber 
provided  with  several  horizontal  plates  is  best  suited  for  this  opera- 
tion. These  plates  are  perforated  with  numerous  small  holes,  upon 
which  rest  tubes  covered  with  a  cap  forming  a  hydraulic  closing, 


234      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

as  in  the  distillation  columns.  The  absorbent  mixture,  contained 
in  a  cylinder  which  is  provided  with  stirrers,  flows  regularly  or  in 
;an  intermittent  manner  into  the  scrubber.  It  comes  to  the  tubes, 
falls  from  one  compartment  to  another,  and  finally  flows  through 
;the  lower  part  of  the  apparatus.  In  circulating  in  this  way  it  meets 
the  gas,  which  flows  in  the  opposite  direction,  the  cyanogen  of  the 
gas  being  thus  removed. 

The  ferrocyanide  solution  is  evaporated  to  dryness,  the  tar  and 
other  impurities  accompanying  it  being  easily  removed  by  redis- 
solving.  The  clear  solution  is  concentrated  and  allowed  to  crys- 
tallize. 

Speaking  concerning  Fowlis'  process  before  the  English  Gas 
Congress  in  1896,  Charles  Hunt  stated  that  he  produces  a  solution 
of  sodium  ferrocyanide  which  on  concentration  and  crystallization 
gives  75%  sodium  ferrocyanide.  One  must  acknowledge  that  that 
is  already  a  splendid  result  setting  well  in  relief  the  profit  which 
may  be  gained  by  the  direct  extraction  of  cyanogen  from  gas. 

Claus  and  Domeier's  Process. — This  process  (1895-96)  is  but  a 
modification  of  Fowlis'  method.  These  investigators  first  pre- 
pare an  absorbent  material  by  fusing  a  mixture  of  iron  or  oxid  of 
iron,  sulphate  of  sodium  or  potassium,  and  charcoal.  The  product 
of  fusion,  taken  up  with  water,  yields  a  grayish-black  substance, 
slightly  soluble,  being  a  compound  of  iron  and  the  alkali  metal 
Fe2Na2S3.  This  substance  is  suspended  in  water  and  placed  in  a 
series  of  washers,  into  which  the  gas,  previously  freed  of  ammonia, 
passes.  Ferrocyanide  and  sulphocyanide  of  sodium  are  formed. 
This  process  does  not  form  much  of  the  latter  salt. 

Schroeder's  Process. — Schroeder  proposes  to  collect  all  the  cya- 
nogen compounds  into  the  ammoniacal  liquors  (French  patent  No. 
281456).  To  the  waters  which  are  used  in  absorbing  the  ammonia, 
ferrous  chloride  is  added.  When  the  gas  passes  through  this  solu- 
tion, the  ammonia  of  the  gas  forms  a  precipitate  of  iron  hydrate, 
Fe(OH)2,  and  ammonium  chloride;  then  the  hydrogen  sulphide 
.  converts  the  hydrated  oxid  of  iron  into  sulphide  of  iron,  which  remains 
.  suspended  in  the  absorption  waters  with  oxid  of  iron;  these  are 
dissolved  by  the  ammonium  cyanide  of  the  gas,  which  converts 
•..them  into  ammonium  ferrocyanide. 

The  liquid  is  distilled  in  the  presence  of  milk  of  lime,  the  ammonia 


MANUFACTURE  OF  FERROCYANIDES.          235 

being  thus  recovered.  Calcium  ferrocyanide,  slightly  soluble,  is 
in  part  precipitated.  To  obtain  the  calcium  ferrocyanide  still  in 
solution  a  current  of  gas  freed  of  ammonia  and  cyanogen  is  con- 
ducted through  the  solution,  the  carbonic  acid  precipitating  the 
lime.  The  small  amount  of  calcium  ferrocyanide  still  remaining 
in  solution  may  be  precipitated  as  Prussian  blue  by  means  of  a 
solution  of  iron  perchloride.  The  precipitate,  consisting  of  cal- 
cium ferrocyanide,  Prussian  blue,  and  carbonate  of  lime,  is  then 
heated  to  boiling  and  treated,  with  constant  stirring,  with  potassa 
or  potassium  carbonate  so  as  to  convert  the  calcium  ferrocyanide 
and  the  Prussian  blue  into  potassium  ferrocyanide,  which,  being 
soluble,  may  be  separated  from  the  insoluble  carbonate  of  lime 
by  filtration.  The  filtered  solution  is  then  concentrated  and  allowed 
to  crystallize. 

Teichmann's  Process. — This  process  is  also  based  on  analogous 
reactions  (French  patent  No.  290265,  June  28,  1890),  but  instead -of 
using  the  chloride,  this  investigator  uses  the  sulphate  of  iron,  and 
in  case  of  need  he  employs  zinc  solutions.  In  using  iron  sulphate 
in  the  washers,  this  salt  becomes  at  once  converted,  by  means  of 
hydrogen  sulphide  and  ammonia,  into  iron  sulphide  and  ammo- 
nium sulphide.  Then  the  cyanide  of  ammonium  acts  on  the  iron 
sulphide,  yielding  ammonium  ferrocyanide. 

The  greater  portion  of  the  cyanogen  thus  goes  into  solution, 
while  a  small  part  of  it  remains  insoluble  in  the  form  of  cyanide 
of  iron.  Sulphide  of  iron  dissolves  just  as  fast  as  ammonium  cyanide 
is  absorbed,  and  by  repeated  additions  of  a  solution  of  iron  sulphate, 
solutions  containing  a  high  percentage  of  ammonium  ferrocyanide 
may  be  obtained. 

The  absorption  apparatus  may  be  inserted  between  the  tar 
extractor  and  the  apparatus  used  in  absorbing  the  ammonia.  With- 
out fear  of  obstruction,  the  ordinary  scrubbers  or  the  standard 
washers  may  be  used.  But,  when  working  on  a  large  scale,  it  is  best 
to  place  the  iron  solutions  in  the  washers. 

The  solutions  of  ammonium  ferrocyanide  obtained  may  be  pre- 
cipitated by  means  of  calcium  chloride. 

The  reaction  is  the  same  when  zinc  salts  are  used.  The  pre- 
cipitated zinc  sulphide  is  converted  by  the  ammonium  cyanide  into 
the  double  cyanide  of  ammonium  and  zinc  and  ammonium  sulphide. 


236      METHODS   OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

By  the  addition  of  other  zinc  salts  to  the  solution  of  the  double 
cyanide,  zinc  cyanide  may  be  precipitated  which  may  be  converted 
directly  into  potassium  cyanide. 

Lewis*  Process. — The  last  process  to  be  mentioned  in  this  class 
is  that  by  Lewis  (Moniteur  Industriel,  1897,  Nos.  26  and  27).  This 
is  based  likewise  on  the  affinity  which  cyanogen  or  hydrocyanic  acid 
has  for  sulphide  of  iron  held  in  suspension  in  an  alkaline  solution, 
the  object  of  the  process  being  to  obtain  a  ferrocyanide. 

Lewis  recommends  that  the  process  be  carried  on  as  follows: 

The  sulphide  of  iron  is  produced  by  precipitating  an  iron  salt  by 
means  of  a.  liquid  prepared  with  the  waste  gases  in  the  treatment 
of  ammonia. 

The  sulphide  of  iron  is  held  in  suspension  in  a  specially  con- 
structed washer,  containing  an  alkaline  solution  in  which  is  an 
excess  of  soluble  iron. 

The  washer  should  be  so  constructed  as  to  aljow  intimate  contact 
of  gas  with  the  suspended  iron,  and  to  avoid  the  formation  of  a 
modified  ferrocyanide,  K7Fe(CN)i2,  which  is  less  stable. 

The  ammonia  should  be  removed  as  thoroughly  as  possible  from 
the  gas  before  the  latter  be  allowed  to  enter  the  washer,  since  the 
acids  of  the  fixed  ammoniacal  salts,  e.g.,  ammonium  chloride,  forms, 
with  the  alkali,  an  alkaline  chloride  which  contaminates  the  product 
obtained. 

By  working  carefully  and  with  an  efficient  system  of  washers 
the  reaction  should  theoretically  be  as  follows: 

2C03K2 + FeS  +  (CNH)  6  =  K4Fe(CN)  6  +  H2S + 2C02 + 2H20. 

But  in  reality,  as  Lewis  has  stated,  there  are  formed  complicated 
and  involved  inter-reactions. 

That  is  the  chief  defect  of  all  the  processes  which  have  been 
reviewed.  Their  perfect  operation  depends  on  numerous  conditions 
chemical  as  well  as  mechanical  or  physical,  which  influence  the 
results  to  a  very  large  extent,  and  unless  great  care  and  many  pre- 
cautions be  taken  in  operating  these  processes,  they  will  be  far  from 
being  successful.  Moreover,  these  processes  all  have  the  disadvan- 
tage of  producing  but  very  dilute  solutions  most  of  the  time,  and 
the  cost  of  treating  such  large  quantities  of  liquids  is  heavy.  These 


MANUFACTURE   OF  FERROCYANIDES.  237 

are  the  reasons  why  these  methods  have  received  but  limited  trials,, 
and  have  never  been  applied  on  a  large  scale. 

Bueb's  Process. — The  process  invented  by  J.  Bueb,  several  years 
ago,  is  entirely  different.  This  process,  now  in  operation  by  the 
Deutsche  Continental  Gas  Gesellschaft  of  Dessau,  has  thus  far 
produced  very  favorable  results.  This  method  will  be  studied 
somewhat  more  at  length,  because  it  is  at  present  in  operation,  and 
because  of  all  the  methods  for  the  direct  extraction  of  cyanogen 
from  gas  this  is  almost  the  only  one  which  deserves  to  be  kept  in 
mind. 

In  fact,  the  reactions  utilized  by  Bueb  are  those  mentioned  in 
the  processes  of  Knublauch  and  others,  but  with  this  difference, 
that  instead  of '  seeking  to  produce  a  soluble  f errocyanide  Bueb 
produces  an  insoluble  compound. 

The  principle  of  this  process  consists  in  bringing  the  gas,  pre- 
viously freed  of  tar,  into  intimate  contact  with  a  saturated  solution 
of  sulphate  of  iron.  The  ammonia  of  the  gas,  playing  the  role  of 
the  alkalis,  used  in  the  other  processes,  a  compound  of  iron,  cyano- 
gen, and  ammonium  is  formed,  which  separates  in  the  form  of  a 
light  mud. 

In  practice,  the  operation  takes  place  in  an  apparatus  specially 
constructed  by  Bueb  on  the  same  principles  as  the  standard 
washers,  with  this  difference,  that  instead  of  flowing  automatically 
into  the  apparatus  the  washing  liquid  passes,  at  definite  intervals, 
from  one  chamber  to  another  by  means  of  a  pump  near  the  washer. 
The  sulphate  of  iron  solution,  previously  prepared  in  a  special  mixer  ^ 
is  pumped  into  the  last  of  the  four  chambers,  then  from  this  one 
to  the  one  preceding,  and  so  on  to  the  first  chamber.  The  cyanogen 
muds,  obtained  in  the  first  compartment  of  the  washer,  are  col- 
lected into  a  forged  iron  reservoir  or  into  a  special  vat,  to  be  trans- 
ferred to  suitable  vessels  if  they  are  to  be  sold  as  such,  or  to  be 
latertreated  in  the  works  itself,  according  to  processes  which  will 
be  mentioned  further  on.  The  first  three  compartments  are 
provided  with  revolving  discs  similar  to  those  of  the  standard 
washers,  while  the  fourth  has  a  stirrer,  the  object  of  which  is  to 
avoid  the  thickening  which  takes  place  in  this  chamber. 

As  these  cyanogen  muds  obtained  by  this  process  contain  appre- 
ciable amounts  of  ammonia  they  may  be  treated  for  the  extrac- 


238       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS 

tion  of  this  product,  especially  if  the  works  have  a  plant  for  their 
treatment.  To  this  end  the  muds  are  heated  to  boiling  by  means 
of  direct  steam  in  boilers  provided  with  stirrers.  The  gas  thus 
liberated  passes  into  a  cooler  where  the  ammonia  condenses  whereas 
the  sulphide  vapors  are  conducted  into  a  purifier.  The  residue  is 
subjected  to  the  action  of  a  filter-press  in  order  to  separate  the 
solution  of  ammonium  sulphate  from  the  insoluble  cyanogen  product. 
The  ammonium  sulphate  solution  which  flows  from  the  filter  is 
concentrated  and  allowed  to  crystallize.  The  insoluble  residue, 
which  is  a  blue  mass  containing  about  30%  Prussian  blue  (44% 
ferrocyanide  of  potassium),  and  4%  ammonia,  is  put  in  tuns  or 
sacks  and  sold  as  such. 

In  communications  made  to  two  successive  annual  Congresses 
of  the  German  Gas  Industries  (Kassel,  1899;  Mainz,  1900)  Bueb 
gives  the  following  details  concerning  the  working  of  his  process: 

The  concentrated  solution  of  iron  sulphate  introduced  into 
the  last  compartment  should  show  about  20°  B.  (That  is,  should 
contain  28%  FeS04  +  7H20.)  In  this  compartment,  which  is  that 
of  the  gas  outlet,  the  gas  contains  only  traces  of  cyanogen,  but 
contains  ammonia  and  hydrogen  sulphide,  which,  coming  in  con- 
tact with  the  iron  sulphate,  converts  it  completely  in  6  to  10  hours 
into  sulphide  of  iron  and  ammonium  sulphate: 

FeS04  +  H2S+2NH3  =FeS  +  (NH4)2S04. 

On  reaching  the  other  compartments  this  solution  of  ammonium 
sulphate,  holding  sulphide  of  iron  in  suspension,  meets  the  gases 
which  are  richer  and  richer  in  cyanogen  and  ammonia,  and  these 
two  bodies  reacting  on  the  sulphide  of  iron  form  with  it  an  insoluble 
double  salt  (NH4)2Fe(CN)6,  while  hydrogen  sulphide  is  set  free, 
and  is  carried  out  of  the  washer,  or  remains  in  part  in  the  product 
of  the  reaction  in  the  form  of  ammonium  sulphide: 

2FeS+6CN.NH4  =  (NH4)2Fe(CN)6+2(NH4)2S. 

This  reaction  is  finished  completely  in  the  first  compartment 
of  the  washer. 

The  reaction  in  its  various  stages  may,  moreover,  be  followed 
by  the  coloration  of  the  absorbent  material.  In  the  last  compart- 
ment, which  contains  the  ir^n  solution,  the  liquid  is  black;  it  becomes 


MANUFACTURE  OF  FERROCYANIDES.  239 

lighter  in  the  others,  and  in  the  first  it  is  greenish  yellow.  The 
cyanogen  mud  which  results  from  this  operation  contains  an 
amount  of  cyanogen  equal  to  18.2%  of  potassium  ferrocyanide 
(Fe(CN)6K4+3H20)  and  to  12.2  to  13.5%  of  Prussian  blue,  besides 
j6  to  7%  of  ammonia,  an  amount  which  represents  about  one  third 
of  the  ammonia  obtained  hi  gas-works. 

If  some  double  salt  still  remains  in  solution  it  may  be  made 
insoluble  by  simply  boiling  and  without  the  addition  of  any  reagent. 
The  yield  by  this  process  is  95%  of  the  cyanogen,  but  the  results 
depend  much  on  the  kind  of  coal  used. 

The  English  coals  are  those  which  contain  the  most  cyanogen. 
They  yield  7.4  grams  of  potassium  ferrocyanide  (Fe(CN)6K4+3Il20) 
per  cubic  meter  of  gas.  In  a  plant  where  a  mixture  of  English  and 
Upper  Silesian  coal  is  used  5.3  grams  are  extracted  per  cubic  meter 
of  gas.  In  another  works  using  a  mixture  of  English  and  Westpha- 
lian  coal  the  yield  was  5.6  grams.  The  coals  of  the  Saar  give  a 
yield  of  4  to  4.5  grams;  those  of  the  north  of  France  4  to  5  grams; 
those  of  the  east  4  grams;  in  general  the  minimum  is  3.5  grams 
and  the  maximum  is  8  grams. 

Furthermore,  Bueb's  process  allows  a  very  simple  removal  of 
hydrogen  sulphide.  Cyanogen  possessing  the  property  of  decom- 
posing the  sulphide  of  iron  recently  formed  by  setting  hydrogen 
sulphide  free,  it  is  evident,  as  Bueb  points  out,  that  this  property 
would  thwart  the  absorption  of  hydrogen  sulphide  by  the  purifying 
materials,  which,  according  to  the  old  processes,  should  play  the 
double  role  of  absorbing  cyanogen  and  hydrogen  sulphide.  There- 
fore, purifying  materials  are  obtained  containing  50-60%  of 
sulphur. 

Bueb  has,  moreover,  observed  that  his  process  gives  a  larger 
yield  the  warmer  his  gas  is,  that  is,  that  the  gas  is  cooled  less  before 
it  passes  through  the  absorption  apparatus.  For  this  purpose 
instead  of  placing  the  coolers,  as  is  usual,  before  the  cyanogen  sepa- 
rators, Bueb  places  them  next  to  these,  i.e.,  between  them  and 
the  scrubbers.  In  this  way  a  smaller  amount  of  ammonia  remains 
in  the  cyanogen  absorption  apparatus,  and  because  of  this  the 
yield  in  cyanogen  compounds  is  again  increased.  Another  advantage 
of  this  new  arrangement  is  that  at  the  high  temperature  at  which 
the  gas  is  kept  the  last  traces  of  tar  and  naphthalene  are  easily 


240      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

removed;  and  to  this  end  Bueb  places  another  vessel  filled  with: 
oil  before  the  cyanogen  'absorption  apparatus  and  connected  with 
it.  This  oil,  being  heated  by  the  passing  gases,  absorbs  more  easily, 
at  this  temperature,  a  larger  amount  of  tar  and  naphthalene. 

Bueb's  process  marks  a  real  progress  in  the  extraction  of  cyanogen 
from  gas,  even  considering  only  the  results  obtained:  Thus  in  the 
dry  way  only  50-60%  of  the  cyanogen  present  in  gas  could  be 
extracted  in  well-conducted  operations,  while  by  this  new  process 
the  yield  is  quantitative.  Moreover,  the  cyanogen  may  be  recovered 
in  a  very  practical  shape,  since  these  products  are  obtained  in  such 
concentrated  form  as  to  warrant  the  expense  of  transportation, 
provided  the  gas-maker  does  not  care  to  convert  them  into  cyanide. 

A.  Smits  of  Amsterdam,  without  knowing  beforehand  the  inves- 
tigations of  Bueb,  in  an  interesting  communication  to  the  Inter- 
national Congress  of  Gas  Industries  in  1900,  confirms  the  results 
obtained  by  the  latter  at  Dessau  by  his  own  experiments  made 
at  the  gas-works  at  Amsterdam  according  to  a  process  similar  to 
that  of«  Bueb. 

Smits  mentions  here  the  reasons  which  led  him  to  absorb  hydro- 
cyanic acid  in  the  presence  of  ammonia  (loc.  cit)  instead  of  bring- 
ing the  gas  previously  freed  of  ammonia  in  contact  with  a  solu- 
tion of  potassium  carbonate  holding  a  ferrous  salt  in  suspension: 

"It  is  remarkable  that  generally  the  absence  of  ammonia  has 
been  considered  as  a  condition  indispensable  for  a  good  absorption 
of  hydrocyanic  acid.  I  suppose  that  we  have  been  led  into  error 
by  the  following  phenomenon:  When  illuminating-gas,  coming  in 
contact  with  the  absorbent  liquid,  contains  ammonia  analysis  shows 
a  less  amount  of  yellow  prussiate  of  potash  in  the  clarified  solution, 
but  after  having  again  analyzed  the  black  precipitate,  which  is  always 
formed  during  absorption,  it  is  easily  proven  that  this  precipitate 
contains  a  quantity  of  cyanogen  which  is  proportional  to  the  amount 
of  ammonia  which  the  gas  contained,  whence  it  follows  that  the 
total  amount  of  hydrocyanic  acid  absorbed  is  in  this  case  greater. 

"  Now  then,  in  this  way  an  amount  of  hydrocyanic  acid  is 
obtained,  which  would  be  lost  during  absorption  in  the  ammonia 
apparatus. 

"  Again,  the  presence  of  ammonia  helps  the  formation  of  an  in- 
soluble cyanide,  and  that  is  the  reason  why  a  smaller  amount  of 


MANUFACTURE  OF  FERROCYANIDES.  241 

yellow  prussiate  of  potash  ie  formed  in  the  liquid  in  the  presence 
of  ammonia." 

"  Those  are  the  reasons  which  led  me  to  suppose  that  the  place 
where  hydrocyanic  acid  was  being  absorbed  was  badly  chosen." 

Starting  with  these  facts,  Smits  sought  to  absorb  the  hydro- 
cyanic acid  by  means  of  a  ferrous  sulphate  solution  at  the  exit  of 
an  apparatus  where  the  gas  still  contains  large  quantities  of  am- 
monia, and  like  Bueb,  he  was  able  to  prove  that  the  yield  was 
quant  ative. 

Thus,  as  may  be  seen,  the  problem  of  the  direct  extraction  of 
cyanogen  from  illuminating-gas  is  really  simple,  and  at  the  same 
time  profitable,  since  it  permits  the  extraction  of  this  cyanogen 
almost  in  its  entirety. 

Feld's  Process. — Finally  shall  be  mentioned  the  process  for  the 
direct  extraction  of  cyanogen  from  gas,  just  recently  patented  by 
Feld  (French  patent  No.  317382,  Sept.  1901),  and  which  certainly 
does  not  lack  in  originality. 

It  consists  in  absorbing  the  cyanogen  in  such  form  that  it  may 
then  be  recovered  by  simply  heating  to  boiling,  in  the  state  of  pure 
hydrocyanic  acid,  which  may  then  be  absorbed  by  ordinary  reagents 
— whereas  the  impurities  of  the  gas  are  either  previously  removed 
or  are  in  great  part  unabsorbed. 

Feld  divides  the  substances  capable  of  absorbing  cyanogen  under 
these  conditions  into  three  groups : 

First  group. — Basic  or  carbonated  compounds,  which  in  aqueous 
solutions,  or  in  suspension  in  water  or  salt  solution,  absorb  hydro- 
cyanic acid,  and  afterwa  d  give  it  off  on  boiling.  These  are  com- 
pounds of  magnesium,  aluminium,  zinc,  manganese,  and  lead.  They 
may  further  be  divided  into  three  subgroups: 

(a)  Those  which  absorb  CNH  and  C02  and  leave  H2S.  These 
:are  basic  compounds  of  magnesium. 

(6)  Those  which  absorb  CNH,  but  neither  C02  nor  H2S.  These 
are  the  basic  compounds  of  aluminium  and  magnesium  carbonate. 

(c)  Those  which  absorb  CNH  and  H2S  but  not  C02.  (Basic 
compounds  of  zinc,  manganese,  and  lead.) 

Second  group. — Compounds  which  in  basic,  neutral,  or  acid 
solution,  or  in  suspension  in  water  or  in  saline  or  acid  solution, 
absorb  hydrocyanic  acid,  and  give  it  up  completely  on  boiling  only 


242       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

in  the  presence  of  acid.  To  this  group  belong  the  compounds  of 
copper,  mercury,  and  the  ferric  and  ferrous  salts.  The  iron  com- 
pounds give  up  the  hydrocyanic  acid  completely  only  when  they 
are  not  intermixed. 

Third  group. — Compounds  which  when  hot  even  in  basic  solution 
or  in  suspension  in  water,  and  in  the  presence  of  salts  of  the  first 
group,  do  not  absorb  hydrocyanic  acid,  but  decompose  hydro- 
sulphuric  acid. 

In  this  group  are  included  ferric  and  ferrous  salts  either  separate 
or  mixed. 

B.    EXTRACTION    OF    CYANOGEN   COMPOUNDS    FROM   THE 
AMMONIACAL    LIQUORS    OF    GAS. 

As  we  have  seen  at  the  beginning  of  this  chapter,  the  ammoniacal 
liquors  contain  a  certain  amount  of  cyanogen  in  the  form  of  ferro- 
cyanide  and  sulphocyanide  of  ammonium.  The  amount  of  the 
former  varies,  on  an  average,  from  150-180  grams,  calculated  as 
Prussian  blue,  per  ton  of  coal.  The  amount  of  ammonium  sulpho- 
cyanide present  in  ammoniacal  liquors  is  quite  variable,  and  depends 
much  on  the  length  of  time  they  have  been  stored.  Thus,  in  the 
same  liquors,  Lewis  found  1.76,  3.5,  and  4  grams  sulphocyanide 
at  intervals  of  one  month.  Generally  one  ton  of  spent  gas-liquorsr 
that  is,  having  been  subjected  to  distillation  of  ammonia,  yields,  on. 
an  average,  6  kg.,  of  ammonium  sulphocyanide. 

Formerly  the  operation  was  carried  on  as  follows:  After  the 
gas-liquors  had  been  distilled  in  the  presence  of  lime  in  order  to 
recover  the  ammonia,  they  were  allowed  to  stand,  and  to  the  clear 
solution  were  added  equal  amounts  of  copper  sulphate  and  iron 
sulphate.  Copper  sulphocyanide  was  thus  formed,  which  was 
decomposed  by  means  of  ammonium  sulphide  with  formation  of 
ammonium  sulphocyanide  (Spence's  process). 

Later  the  ammonium  sulphide  was  replaced  by  barium  sulphide. 

Pendrie's  Process. — The  object  of  this  invention  (French  patent 
No.  189648,  March  28,  1888)  is  to  recover  the  cyanogen  compounds 
of  the  ammoniacal  liquors  in  the  form  of  Prussian  blue. 

The  residues,  after  the  distillation  of  the  ammonia,  are  allowed 
to  stand  until  clarified  and  then  decanted.  Ordinary  sulphuric 
acid  is  then  added  to  acid  reaction  in  order  to  remove  any  hydrogen 


MANUFACTURE  OF  FERROCYANINES.  243' 

sulphide  contained  therein.  A  portion  of  the  hydrogen  sulphide 
is  set  free,  another  portion  is  decomposed.  The  whole  is  allowed 
to  stand  24  hours,  during  which  the  sulphur  and  sulphate  of  lime 
settle.  The  solution  is  decanted,  and  to  the  liquid  is  added  a  suit- 
able quantity  of  a  ferric  salt,  Prussian  blue  being  precipitated 
This  may  be  converted  into  potassium  ferrocyanide,  after  having 
first  decanted  the  solution,  and  allowing  the  Prussian  blue  to  stand 
in  contact  several  days,  with  a  lye  made  of  caustic  potash  or  potas- 
sium carbonate. 

Bower's  Process. — Bower  (German  patent  of  Dec.  23,  1895), 
recommends  the  precipitation  of  ferrocyanides  and  sulphocyanides, 
by  means  of  a  copper  salt  in  order  to  form  insoluble  ferrocyanide 
and  sulphocyanide  of  copper.  A  mixture  of  these  two  salts,  when 
treated  with  iron,  yields  on  the  one  hand  insoluble  ferrocyanide 
of  iron,  and  on  the  other  soluble  sulphocyanide,  which  may  there- 
fore be  easily  separated.  In  practice  Bower  recommends  carrying 
on  the  process  as  follows: 

Before  distilling,  the  ammoniacal  liquors  are  treated  with  mag- 
netic iron  either  alone  or  with  the  addition  of  an  iron  salt,  in  suffi- 
cient quantity  to  convert  all  the  cyanogen  into  the  form  of  ferro- 
cyanide and  sulphocyanide  of  iron. 

The  liquors  are  then  distilled  in  the  presence  of  quicklime  in 
a  boiler  provided  with  a  stirrer.  The  residual  liquors,  containing* 
ferrocyanide  and  sulphocyanide  of  calcium,  are  then  treated  with 
a  solution  of  cuprous  chloride  in  sufficient  quantity  to  precipitate 
the  whole  of  the  cyanogen  compounds  as  insoluble  salts. 

The  precipitate  is  collected,  washed,  and,  while  still  moist,  treated 
with  finely  divided  iron.  The  iron  replaces  tne  copper,  yielding 
insoluble  ferrocyanide,  and  soluble  sulphocyanide.  These  ara 
separated  by  filtration. 

The  ferrocyanide  of  iron  is  then  treated  at  the  boiling-point^ 
with  an  alkali,  in  order  to  obtain  a  soluble  alkali  ferrocyanide,  which 
is  purified  by  crystallization.  The  solution  of  sulphocyanide  is. 
concentrated  and  allowed  to  crystallize. 

Lewis'  Process. — Somewhat  different  is  the  process  of  Lewis 
and  Cripps  (English  patent  No.  5184,  March  7,  1896),  the  method  of 
procedure  of  which  is  as  follows:  After  distilling  off  the  ammonia 
by  the  usual  method  with  lime,  the  residual  liquors  contain  the 


244      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

ferrocyanide  and  the  sulphocyanide  in  the  form  of  lime  salts 
(CNS)2CaandCa2Fe(CN)6.  This  liquor  flows  from  the  stills  into 
a  suction  reservoir  whence  a  pump  drives  it  to  the  top  of  a  tower, 
filled  with  pieces  of  coke  or  brick,  through  which  it  filters,  encounter- 
ing on  its  way  down  an  inverse  current  of  sulphurous  acid  and  car- 
bonic acid,  which  is  obtained  by  passing  the  waste  gases  of  an  ammo- 
nia distillation  over  a  grate  which  burns  the  hydrogen  sulphide 
and  converts  it  into  sulphurous  acid.  The  action  of  this  gaseous 
current  neutralizes  and  acidifies  the  originally  alkaline  liquid.  On 
emerging  from  the  tower  the  acid  solution  flows  into  a  long  reservoir 
divided  into  two  unequal  compartments.  The  solution  first  comes 
to  the  larger  compartment  where  it  is  treated  with  a  solution  con- 
taining ferrous  and  ferric  salts  in  order  to  precipitate  the  ferro- 
cyanide as  Prussian  blue.  The  liquid  passes  from  one  compart- 
ment into  the  other,  thus  allowing  the  Prussian  blue  precipitate 
time  in  which  to  settle.  The  supernatant  liquid  then  flows  into 
a  special  reservoir,  there  to  be  treated  with  a  view  to  the  recovery 
of  the  sulphocyanides. 

For  this  purpose  a  copper  sulphate  solution  is  added  to  the 
liquid,  there  being  formed  an  insoluble  white  precipitate  of  cuprous 
.sulphocyanide: 

Ca(CNS)  2 +S03H2 +2CuS04  +  H20 =Cu2(CNS)  2 +CaS04  +2H2S04. 

The  previous  treatment  with  sulphurous  acid  is  absolutely  necessary, 
otherwise  there  would  be  formed  a  partially  soluble  black  copper 
sulphocyanide. 

The  cuprous  sulphocyanide  precipitate  is  separated  by  decanta- 
tion  and  washed.  It  is  treated  with  a  solution  of  alkali  sulphydrate 
which  forms  a  soluble  alkali  sulphocyanide  and  an  insoluble  copper 
sulphide.  The  alkali  hydrosulphate  is  likewise  obtained  by  utilizing 
the  waste  gas  of  an  ammonia  distillation,  these  gases  passing  through 
a  washer  filled  with  a  strong  caustic  alkali  solution.  When  the 
copper  sulphide  is  exposed  to  air  and  then  treated  with  an  acid,  the 
copper  salt  employed  in  the  precipitation  is  "revivified/  and  may 
be  used  over  again. 


MANUFACTURE  OF  FERROCYANIDES.  245 

C.    THE    EXTRACTION   OF    CYANOGEN    COMPOUNDS    FROM   THE 
PURIFYING   MATERIALS   OF   GAS. 

The  purifying  materials  which  are  used  for  the  chemical  purifica- 
tion of  gas  still  constitute,  in  the  works  where  the  direct  extraction 
of  the  cyanide  compounds  is  not  in  operation  (arid  they  are  the 
larger  number) ,  an  important  source  of  these  products.  As  has  already 
been  seen,  these  materials  contain  almost  the  whole  of  the  cyanogen 
formed  during  the  manufacture  of  gas,  and  it  has  likewise  been 
shown  that  the  other  impurities,  especially  hydrogen  sulphide,  are 
also  absorbed  therein. 

The  composition  of  the  purifying  materials  varies  in  different 
works  and  in  different  countries.  Generally  mixtures  of  lime  and 
ferrous  sulphate  or  oxid  of  iron  are  still  used.  In  Germany  and  in 
Belgium,  purifying  materials  are  used  on  a  large  scale,  composed 
entirely  of  artificial  oxids  of  iron,  especially  the  brown  oxid,  known 
under  the  name  of  limonite.  The  hydrated  and  moist  oxid  seems 
to  be  preferable  for  the  absorption.  Below  the  composition  of  two 
limonites  is  given: 

I.  II. 

Holland.  Belgium. 

Sesquioxid  of  iron 51 . 30  59 . 14 

Alumina 1 . 17  0. 98 

Lime  and  magnesia 1 . 63  0 . 59 

Silica 4.97  5.23 

Organic  substances 26 . 26  19 . 64 

Water 14.02  15.13 

Loss  and  undetermined 0. 63  1 . 09 

These  purifying  materials  are  converted,  on  account  of  the 
passage  of  gas  through  them,  into  sulphur,  sulphide  of  iron,  ferrous 
ferrocyanide,  sulphocyanide  of  iron,  etc.,  and  the  moment  neces- 
sarily arrives  when  they  become  inactive.  In  order  to  revivify 
them  they  are  spread  out  on  a  flat  surface,  where  they  are  constantly 
stirred  with  a  shovel.  The  oxygen  of  the  air  converts  the  inactive 
sulphide  of  iron  into  the  active  oxid  and  sulphur, 


and  the  ferrous  ferrocyanide  into  Prussian  blue.     The  same  mix- 
ture may  be  revivified  several  times,  the  result  being  that  an  appre- 


246   METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

ciable  part  of  the  oxid  of  iron  becomes  converted  into  Prussian 
blue  (which  may  be  recognized  by  the  greenish-blue  color  which 
the  materials  assume)  and  the  sulphur  accumulates  in  such  quan- 
tities (30  to  40%)  that  the  mixture  no  longer  exerts  any  purifying 
action. 

It  is  hi  this  'state  that  it  is  known  as  spent  oxid,  which  is  immedi- 
ately treated  or  more  generally  sold  to  manufacturers  of  Prussian 
blue  or  of  prussiates. 

Its  composition  varies  naturally  according  to  a  great  many 
circumstances:  kind  of  coal  distilled,  method  of  distillation,  the 
composition  of  the  purifying  materials,  the  degree  of  fineness  of 
the  same,  the  method  of  revivification,  etc. 

According  to  Esop,  the  sulphocyanic  content  varies  from  0.39 
to  4.25%,  the  potassium  ferrocyanide  from  3.02  to  4.58%,  the 
ammonia  from  0.49  to  4.38%.  Below  are  given  some  analyses  of 
purifying  materials. 

ANALYSES  OF  SOME  SPENT  OXIDS. 
LAMING  MIXTURE. 

Sulphur 41.79% 

Prussian  blue 7.37 

Sulphocyanic  acid 3.01 

Hydroferrocyanic  acid 1.01 

LUX   MASS. 

Sulphur 40.75% 

Prussian  blue 3.08 

Ammonium  sulphocyanide 5. 14 

Ammonia 2.  23 

NATURAL  OXID   OF. IRON. 

I.  II. 

Sulphur 30.58%  30.03% 

Prussian  blue 6.30          8.62 

Ammonium  sulphocyanide 4.08          2. 12 

Ammonia 0.41  1.30 

Formerly  the  spent  oxids  were  considered  as  useless  residues, 
but  manufacturers  have  learned  how  to  derive  benefit  therefrom, 


MANUFACTURE  OF  FERROCYANIDES. 


247 


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248       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

and  to-day  they  are  treated  with  a  view  to  the  extraction  frcm 
them  of  sulphur  ammonium  sulphate  'and  cyanogen  compounds. 

Gauthier-Bouchard's  Process. — To  Gauthier-Bouchard  is  due 
the  idea  of  utilizing  the  purifying  materials  for  the  manufacture 
of  potassium  ferrocyanide.  This  process,  which  was  set  up  in  a 
works  at  Aubervilliers,  was  operated  as  follows: 

The  materials  were  first  subjected  to  lixiviation  with  cold  water 
for  the  purpose  of  removing  all  the  soluble  salts  (sulphocyanide 
of  iron  and  ammonium  and  the  ammonia  salts).  The  insoluble 
residue  was  intimately  mixed  with  hydrated  lime  in  the  propor- 
tion of  30  kg.  of  lime  per  cubic  meter  or  1600  kg.  of  washed  mate- 
rials. Water  was  added  and  the  whole  stirred.  After  standing 
several  hours,  the  mixture  was  again  lixiviated  with  cold  water. 

The  residues  obtained  from  these  washings  are  exposed  to  the 
air  for  3  or  4  months  and  again  treated  with  water.  The  wash- 
waters  contain  ferrocyanides  in  the  fprm  of  lime  salt.  The  first 
washings,  which  are  more  concentrated,  are  treated  with  potassium 
carbonate,  there  being  formed  insoluble  carbonate  of  lime,  whereas 
the  potassium  ferrocyanide  remains  in  solution.  This  latter  is 
decanted,  concentrated,  and  crystallized.  The  final  washings, 
which  are  too  dilute  to  be  thus  profitably  treated,  are  treated  with 
a  solution  of  iron  protosulphate;  a  white  precipitate  of  ferrocyanide 
of  iron  is  formed,  which  on  standing  in  the  air  becomes  converted 
into  Prussian  blue. 

In  his  works  at  Aubervilliers,  Gauthier-Bouchard  succeeded,  by 
this  process,  in  extracting  22,500  kg.  of  Prussian  blue  from  the 
1500  cu.m.  of  spent  oxid  furnished  him  by  the  Parisian  gas  company, 
or  an  average  of  15  kg.  per  cubic  meter.  The  potassium  ferro- 
cyanide produced  by  the  Gauthier-Bouchard  process  brought  275 
francs  per  100  kg.  And  yet,  while  recognizing  the  advantages  of 
this  process,  most  of  the  investigators  of  that  time  preferred  the 
ignition  of  the  nitrogenous  organic  substances,  notwithstanding 
the  empiricism  and  the  imperfections  of  this  latter  process. 

At  present  the  Gauthier-Bouchard  process,  somewhat  modi- 
fied, is  in  operation  in  Camille  ArnouFs  works  at  St.-Ouen- 
1'Aumone,  where  it  was  installed  in  1875. 

Moreover,  almost  all  the  processes  which  treat  the  spent  oxids 
with  a  view  to  the  recovery  of  the  cyanogen  compounds  are  modi- 


MANUFACTURE  OF  FERROCYANIDES.  249 

fications  of  the  Gauthier-Bouchard  process.  The  improvements 
made  in  the  process  refer  especially  to  the  treatment  with  water 
and  to  the  conversion  into  potassium  ferrocyanide. 

The  processes  at  present  in  use  differ  very  little.  They  may 
be  divided  into  two  groups: 

The  first  group  includes  those  processes  in  which  the  spent  oxid 
is  previously  treated  with  carbon  bisulphide  in  order  to  remove 
the  sulphur  which  is  present  in  rather  large  quantities. 

In  the  second  group  the  cyanogen  compounds  are  immediately 
extracted.  These  are  the  ones  which  are  mostly  in  use,  and  they 
will  now  be  studied.  Their  operation  may  be  divided  into  three 
principal  stages: 

(1)  Lixiviation  of  the  materials  in  order  to  remove  the  soluble 
salts   (ammoniacal  salts  and  sulphocyanides)   and  to  recover  the 
ammonia  and  the  sulphocyanides. 

(2)  Conversion  of  the  insoluble  ferrocyanides  into  soluble  ferro- 
cyanides  (sodium  and  calcium). 

(3)  Conversion  of  the  calcium  or  sodium  ferrocyanide  into  that 
of  potassium. 

(1)  LIXIVIATION. — As  has  just  been  remarked  the  object  of  this  is 
to  remove  the  soluble  salts,  which  consist  especially  of  ammonium 
sulphate,  sulphocyanides  of  ammonium  and  iron,  and  some  iron 
sulphate.  The  lixiviation  of  the  materials  takes  place  in  filtering- 
vats  arranged  generally  in  series  of  eight  on  stands  or  blocks.  These 
vats  may  be  of  iron,  though  ordinarily  they  are  made  of  wood,  and 
are  2  meters  square  and  0.90  meter  high,  their  capacity  being  about 
3000  kg.  spent  oxid.  They  are  fitted  up  with  a  false  bottom,  consist- 
ing of  a  wooden  frame  B  (Fig.  19)  resting  on  wooden  beams.  This 
frame  is  covered  with  a  layer,  10  cm.  in  depth,  of  twigs  or  straw  (A) 
and  this  layer  is  itself  covered  with  a  cotton  or  jute  filtering-cloth  D. 
A  tap  R  allows  the  liquid  of  the  false  bottom  to  flow  into  a  wooden 
or  cement  trench  which  communicates  by  openings,  closed  with 
plugs,  with  three  cisterns  (A,  B,  C)  (Fig.  20). 

The  lixiviation  is  carried  on  as  follows:  The  purifying  mate- 
rials are  first  shoveled  into  the  vats  and  water  is  then  allowed  to 
flow  into  vat  No.  1  so  as  to  cover  the  materials  to  the  extent  of  a 
few  millimeters  only.  This  is  allowed  to  stand  12-24  hours,  at 
the  end  of  which  time  the  liquor  is  drawn  off  into  the  trench  and 


250      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 


collected  in  the  cistern  A,  and  from  there  it  is  pumped  into  vat 
No.  2,  at  the  same  time  vat  No.  1  is  treated  with  a  fresh  supply 
of  water.  The  water  is  again  allowed  to  stand  in  contact  with 
the  materials  for  24  hours,  when  the  liquid  is  withdrawn  from  vat 
No.  2  and  collected  in  cistern  B,  from  which  it  is  pumped  into  vat 
No.  3.  The  liquid  is  also  drawn  off  from  vat  No.  1  into  cistern  A, 
from  which  it  is  pumped  into  vat  No.  2,  and  so  on.  At  the  end 
of  the  treatment  the  strong  liquors  show  10-14°  B.  and  contain 


FIG.  19. 

about  40  grams  of  ammonia  per  liter.  The  pump  transfers  the 
liquid  from  cistern  C  to  an  upper  reservoir,  where  it  will  be  taken 
up  again  and  distilled  with  lime  in  order  to  obtain  the  ammonia. 
This  is  done  in  the  usual  way  and  with  the  ordinary  apparatus 
used  in  the  recovery  of  ammonia  from  the  ammoniacal  liquors. 
After  the  distillation,  there  remains  in  solution  calcium  sulpho- 
cyanide,  which  is  later  converted  into  potassium  sulphocyanide. 

(2)  CONVERSION  OF  THE  INSOLUBLE  INTO  THE  SOLUBLE  FERRO- 
CYANIDES. — This  may  be  carried  on  in  two  ways: 

(a)  In  an  apparatus  fitted  up  with  a  stirrer,  similar  to  that  in 
Fig.  21. 

(&)  In  filtering-vats  similar  in  every  respect  to  those  used  in  the 
lixiviation  of  the  materials. 

The  former  apparatus,  provided  with  a  stirrer,  is  generally  a 


MANUFACTURE  OF  FERROCYANIDES. 


251 


252   METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS 


AZH' 


FIG.  21. — Apparatus  Fitted  with  a  Stirrer  for  the  Conversion  of  the  Insoluble 
Cyanides  into  the  Soluble. 


MANUFACTURE  OF  FERROCYANIDES.  253 

kettle  or  boiler  made  of  10-mm.  cast  iron,  with  a  capacity  of  6000 
liters,  and  ordinarily  receiving  2000-3000  kg.  spent  oxid.  First,  the 
dilute  lixivium  is  conducted  into  the  apparatus  and  then  2000-3000 
kg.  of  the  materials  are  added.  The  stirrer  is  set  in  motion,  the 
whole  being  heated  with  steam.  The  mud-like  mass  flows  into  the 
filter-presses  in  order  to  separate  the  solution  which  contains  20-50 
grams  of  ferrocyanide,  expressed  as  potassium  ferrocyanide,  per  liter. 

The  mass  is  first  pulverized  with  a  specially  constructed  powder, 
then  sifted  through  a  4-mm.  sieve,  mixed  with  lime  and  soda  in 
amounts  varying  with  the  composition  of  the  mass  (which  has  been 
previously  analyzed)  and  then  treated  in  the  boiler. 

When  using  the  filtering-vats  the  operation  is  carried  on  as  follows: 

After  having  been  subjected  to  the  first  lixiviation  the  materials 
are  allowed  to  stand  several  days  in  order  to  drain.  They  are  then 
spread  upon  asphalt  or  cement  surfaces  so  as  to  dry  them.  The 
drying  may  be  hastened  by  frequently  turning  the  mass  about  with 
a  shovel,  this  turning  also  serving  to  break  the  lumps.  When  the 
mass  is  dry  it  is  sifted  through  a  4-mm.  sieve,  then  the  sifted 
mass  is  mixed  intimately  with  powdered  slack  lime,  in  amounts 
carefully  determined  by  a  previous  analysis  of  the  mass.  Then  the 
filtering-vats,  which  are  arranged  as  in  the  first  lixiviation,  are  charged 
with  this  mixture,  and  water  is  added  so  as  to  cover  the  materials 
to  the  extent  of  a  few  millimeters.  It  is  allowed  to  stand  12  to 
24  hours,  and  the  operation  is  carried  on  as  in  the  first  lixiviation. 
Generally  eight  or  ten  vats  are  used,  and  lixiviums  are  obtained  show- 
ing 12-14°  B.,  containing  from  120-140  grams  of  Fe  (CN6)K4  + 
3H20  per  liter,  whereas  with  the  stirring  apparatus  the  solutions 
contained  but  40-50  grams  of  Fe(CN)6K4. 

(3)  PRECIPITATION  OF  FERROCYANIDES. — The  lixiviums  obtained 
by  using  the  stirring  apparatus  contain  ferrocyanide  of  calcium  and 
sodium,  whereas  those  which  are  produced  by  the  filtering-vats 
contain  the  whole  of  the  ferrocyanide  in  the  form  of  calcium  fer- 
rocyanide, Ca2Fe(CN)6.  Both  of  them  likewise  contain  sulpho- 
cyanide  of  calcium  and  ammonium.  The  object  of  the  following 
treatment  is  to  precipitate  the  ferrocyanides,  and  this  may  be  done 
in  one  of  three  ways: 

(a)  By  means  of  iron  salts. 

(6)  By  means  of  ammoniacal  salts. 


254      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

(c)  By  means  of  potassium  chloride. 

Precipitation  by  Means  of  Iron  Salts. — This  consists  simply  in 
precipitating  the  ferrocyanides  in  the  form  of  Prussian  blue.  If  the 
lixiviums  contain  the  calcium  ferrocyanide  they  are  treated  with 
ferrous  or  ferric  chloride;  if,  on  the  other  hand,  they  contain  sodium 
ferrocyanide,  sulphate  of  iron  is  used. 

The  solution  obtained  with  the  stirring  apparatus  always  contains 
sulphides,  and  on  account  of  the  presence  of  free  ammonia  they  are 
alkaline.  The  solutions  are  acidified  in  a  special  vat  and  are  allowed 
to  stand  in  order  that  the  sulphur  may  separate  out;  after  which  the 
clear  liquid  is  decanted  and  subjected  to  precipitation  with  an  iron 
salt. 

On  account  of  being  cheaper,  the  use  of  the  ferrous  salts 
(FeCl2  or  FeSOJ  is  preferred,  the  precipitate  being  oxidized  in 
air.  Precipitation  is  carried  on  in  wooden  or  iron  vats,  the  iron 
solution  being  gradually  a$ded,  stirring  the  while,  and  from  time 
to  time  a  sample  of  the  liquors  is  tested  to  make  sure  that  the  pre- 
cipitation is  complete.  When  this  point  is  reached  the  whole  is 
allowed  to  stand  at  least  24  hours,  and  then  the  supernatum  liquid 
is  drawn  off.  The  Prussian  blue  is  subjected  to  the  filter-presses 
and  then  converted  into  potassium  ferrocyanide  by  treatment  with 
potash  or  with  potassium  carbonate. 

Precipitation  by  Means  of  Ammoniacal  Salts. — This  process  is  based 
on  the  insolubility  of  the  double  salt  Ca(NH4)2Fe(CN)6: 

Ca2Fe(CN)6  +2NH4C1 =Ca(NH4)2Fe(CN)6  +CaCl. 

Sal  ammoniac  as  such  is  never  used;  but  instead  the  operation 
is  carried  on  in  such  a  way  that  the  salt  is  produced  in  sufficient 
amount  at  the  time  of  the  precipitation  by  taking  care  to  obtain 
lixiviums  which  contain  enough  ammonia  so  that  it  will  be  necessary 
to  neutralize  them  with  hydrochloric  acid.  It  is  well  for  this  pur- 
pose to  add  to  the  lixiviated  materials  a  small  amount  of  a  mix- 
ture of  non-lixiviatd  materials  and  lime,  which  will  produce  the 
ammonia  necessary  to  the  reaction.  The  operation  is  carried  on 
in  a  stirring  apparatus  which  is  kept  constantly  in  motion,  hydro- 
chloric acid  being  added  until  the  reaction  is  acid.  The  whole 
is  then  heated  to  80°  when  the  double  salt  separates  out  as  a  white 


MANUFACTURE  OF  FERROCYANIDES.  255 

powder  with  a  slight  bluish  tint.  When  the  precipitation  is  finished, 
the  stirring  is  stopped  and  the  precipitate  allowed  to  settle.  The 
clear  liquid  is  drawn  off,  the  precipitate  being  subjected  to  the 
filter-press.  As  the  double  salt  is  not  entirely  insoluble  in  water 
(there  remaining  3.75  grams  per  liter  at  25°)  it  is  well  to  precipitate 
the  mother  liquors  in  the  form  of  Prussian  blue  by  means  of  an 
iron  salt. 

The  double  salt  Ca(NH4)2Fe(CN)6  may  be  treated: 

(1)  With  lime,  in  a  stirring  apparatus,  so  as  to  produce  pure 
calcium  f  errocy  anide, 

Ca(NH4)2Fe(CN)6  +CaO =Ca2Fe(CN)6 +2NH3  +H20, 
which  may  then  be  converted  into  potassium  ferrocyanide  by  pre- 
cipitating   a   double  salt    CaK2Fe(CN)6    by  means  of    potassium 
chloride,  and  then  converting  this  double  salt  into  potassium  fer- 
rocyanide by  boiling  with  potassium  carbonate: 

CaK2Fe(CN)  6 + C03K2  =  KJFeCCN)  6 + CaC03. 

(2)  With  potassium  carbonate  in  the  presence  of  lime: 
Ca(NH4)  2Fe(CN)6 +2C03K2 + CaO 

=K4Fe(CN)6 +2CaC03  +2NH3  +H20. 

In  this  way  solutions  of  potassium  ferrocyanide  are  obtained 
which  are  concentrated  to  30°  B.  and  then  allowed  to  crystallize. 

Precipitation  by  Means  of  Potassium  Chloride. — This  reaction 
gives  rise  to  the  formation  of  a  slightly  soluble  double  salt, 
CaK2Fe(CN)6: 

Ca2Fe(CN)6 +2KC1 =CaK2Fe(CN)6  +CaCl2. 

The  precipitation  may  be  done  either  directly  in  the  calcium 
ferrocyanide  solutions  containing  at  least  100  grams  of  K^Fe^N)  e, 
or  in  the  same  solutions  after  concentration  to  20-25°  B.  The 
'Operation  is  carried  on  at  80°  in  a  small  kettle  or  boiler  provided 
with  a  stirrer.  An  excess  of  potassium  chloride,  added  in  the  form 
of  crystals,  should  be  used.  The  double  salt  CaK2Fe(CN)e  is  pre- 
cipitated as  a  light-yellow  powder,  which  may  be  separated  by 
decantation  or  filtration,  and  then  washed  with  water,  and  finally 
treated  with  potassium  carbonate  so  as  to  obtain  ferrocyanide  of 
potassium  according  to  the  reaction 

CaK2Fe(CN)6 +C03K2 =C03Ca +K4Fe(CN)6. 


256       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

RECOVERY  OF  THE  SULPHOCYANIDES. — These  are  found  in  the 
waters  of  the  first  lixiviation  in  the  form  of  calcium  sulphocyanide. 
They  may  be  extracted  by  treating  the  residual  solutions  from  the 
ammonia  distillation  by  precipitation  with  a  sodium  or  potassium 
salt,  concentration  and  crystallization.  They  may  also  be  precipitated 
in  the  form  of  copper  sulphocyanide,  which  is  then  decomposed  by 
alkaline  sulphide.  The  same  mode  of  treatment  is  applicable  to  other 
residual  solutions  containing  sulphocyanides. 

In  other  works,  sulphur  which  is  always  present  in  these  masses 
in  amounts  varying  generally  from  30%  to  40%,  but  sometimes 
reaching  60%  and  more,  is  first  of  all  extracted.  Various  means 
may  be  used  in  bringing  this  about :  carbon  bisulphide,  or  oil  of  tar 
may  be  used.  In  other  works  the  sulphur  is  extracted  by  fusion 
with  water  under  high  pressure  in  close  dboilers.  Finally,  a  works 
at  Marseilles  withdraws  the  sulphur  by  means  of  superheated  steam 
obtaining  in  this  way  flowers  of  sulphur. 

But  the  sulphur  which  is  obtained  by  these  various  methods  is 
always  more  or  less  dark  in  color  due  to  the  tarry  substances,  which 
prevents  its  use  as  a  commercial  and  industrial  product.  All  in 
all,  this  extraction  can  but  give  a  small  profit,  and  therefore  it  is 
but  little  used.  The  works  which  carry  on  the  extraction  of  sulphur 
prefer  subjecting  the  spent  oxides  to  ignition  in  layer-kilns,  according 
to  the  Maletra  system  for  the  extraction  of  cyanide  compounds. 
The  sulphurous  acid  thus  formed  is  utilized  in  the  production  of  sul- 
phuric acid.  There  is  one  objection  to  this,  which  is  that  the  sul- 
phurous acid  is  mixed  with  carbonic  acid  produced  by  the  car- 
bonization of  the  tar  products,  and,  on  the  other  hand,  a  part  of  the 
sulphurous  acid  is  continued  with  the  lime  which  is  always  in  excess 
in  the  exhausted  and  treated  materials. 

Moreover,  various  methods  have  been  proposed  for  the  extraction 
of  cyanogen  compounds  from  purifying  materials,  but  very  few  of 
them  have  been  tried  on  an  industrial  scale;  they  will,  however,  be 
passed  in  review. 

Valentin's  Process.— Valentin  (English  patent  No.  3908,  Nov.  12, 
1874)  recommended  treating  the  materials  with  water  in  order  to 
remove  the  soluble  salts,  and  then  to  treat  the  residues  of  this  wash- 
ing with  carbonate  of  lime  or  magnesia,  or  a  mixture  of  the  two, 
at  the  boiling-point.  There  are  thus  formed  ferrocyanides  of  mag- 


MANUFACTURE  OF  FERROCYANIDES.  257 

nesium  and  of  calcium,  which  remain  in  solution,  and  which  may 
then  be  precipitated  in  the  form  of  Prussian  blue. 

Harcourt's  Process. — Harcourt  (1875)  first  treats  the  materials 
with  sulphuric  acid,  the  sulphates  of  iron  andjimmonium  dissolving, 
whereas  the  sulphur  and  the  Prussian  blue  remain  insoluble.  The 
Prussian  blue  is  separated  by  means  of  ammonia  and  reprecipitated 
from  the  solution  with  an  iron  salt.  Harcourt  converts  the  sulpho- 
cyanides  into  ammonium  sulphate  by  means  of  sulphuric  acid  and 
manganese  dioxid. 

Kunheim's  Process. — Kunheim  and  Zimmermann  (German  patent 
No.  26884,  July  6,  1883)  remove  the  sulphur  and  the  soluble  substances 
from  the  materials,  which  are  then  pulverized,  sifted,  and  mixed 
with  lime,  and  treated  as  follows:  The  mixture  is  heated  in  a  closed 
vessel  at  a  temperature  between  40°  and  100°;  the  ammonia,  united 
to  the  ferrocyanogen,  distills  and  is  collected.  The  solution  of 
calcium  ferrocyanide  obtained  is  treated  in  the  usual  way  in  order 
to  convert  it  into  Prussian  blue,  or  else  evaporated  and  treated  with 
potassium  chloride  in  order  to  form  a  double  cyanide  CaK2Fe(CN)6, 
which  may  then  be  converted  into  potassium  ferrocyanide  by  means 
of  potassium  carbonate.  The  materials,  mixed  with  lime,  may 
also  be  treated  directly  with  water,  thus  obtaining  an  ammoniacal 
solution  of  calcium  ferrocyanide,  which  on  careful  treatment  under 
definite  conditions,  in  the  warmth,  yields  a  precipitate  of  ferro- 
cyanide of  calcium  and  ammonium  difficultly  soluble  in  water. 
When  this  precipitate  is  treated  in  a  closed  ves*sel  with  lime  it 
yields  pure  calcium  ferrocyanide,  while  the  ammonia  distills  off. 
The  calcium  ferrocyanide  is  then  converted  into  Prussian  blue,  or 
into  yellow  prussiate  by  the  ordinary  methods. 

HempePs  Process. —  The  process  of  Hempel  and  Steinberg 
(German  patent  No.  33936,  Nov.  21,  1884)  consists  in  first  extracting 
the  masses  with  water  at  60°  C.,  and  then  treating  them  at  the 
ordinary  temperature  with  a  10%  ammonia  solution  in  quantities 
four  or  five  times  more  than  sufficient  to  convert  them  into  ammo- 
nium ferrocyanide,  which  latter  is  then  converted  into  Prussian  blue 
or  yellow  prussiate. 

Wolfram's  Process. — In  this  process  (German  patent  No.  40215, 
Nov.  14,  1886)  the  masses  are  first  treated  with  dilute  sulphuric  or 
hydrochloric  acid.  The  acid  solution  thus  obtained  is  neutralized 


258      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

with  oxid  of  iron.  The  ammonium  sulphocyanide  is  thus  decom- 
posed, as  is  likewise  the  ammonium  f errocyanide ;  sulphate  of  ammo- 
nium is  formed,  whereas  Berlin  blue,  sulphur,  and  hydroferrocyanic 
acid  are  precipitated.  Sulphur  is  extracted  by  means  of  carbon 
bisulphide  in  suitable  apparatus. 

Donath's  Process.  —  Donath  and  Ornstein's  process  (German 
patent  No.  110097,  May  29,  1898)  is  based  on  the  characteristic  which 
Berlin  blue  possesses  of  dissolving  in  concentrated  hydrochloric  acid, 
and  being  reprecipitated  when  the  solution  is  evaporated  or  when 
it  is  allowed  to  stand  in  air.  The  materials  are  first  treated  with 
very  dilute  acid  so  as  to  dissolve  the  oxid  of  iron.  The  residue  is 
dried,  and  treated  with  concentrated  hydrochloric  acid,  the  Berlin 
blue  dissolving  and  imparting  to  the  solution  a  light-yellow 
color.  It  is  precipitated  from  this  solution  by  the  addition  of 
water,  the  precipitate  appearing  in  the  form  of  small  crystalline 
needles. 

Richter's  Process.— Richter  (French  patent  No.  196144,  1889) 
begins  by  heating  the  materials  in  closed  vessels  by  means  of  a  stream 
of  water- vapor.  The  ammonia  which  is  set  free  is  collected  in  sul- 
phuric acid.  The  residue  is  likewise  treated  in  a  closed  vessel  with 
hydrochloric  acid  so  as  to  obtain  iron  perchloride.  The  residue  from 
this  treatment  is  then  mixed  with  magnesium  carbonate  and  treated 
with  water  in  order  to  extract  the  magnesium  ferrocyanide  which 
may  be  converted  by  the  ordinary  methods. 

Esop's  Process.  —  Esop  recommends  (Ztseh.  fur  angewandte 
Chemie  1889)  digesting  the  masses  with  water  and  then  subjecting 
them  to  the  filter-press,  the  residue  being  treated  with  lime  and 
sodium  sulphate,  a  mixture  which  it  seems  gives  better  results  than 
lime  alone. 

Marasse's  Process. — Marasse  of  Berlin  converts  the  whole  of  the 
ferrocyanide  of  the  purifying  materials  into  sulphocyanides  (French 
patent  No.  158731,  Nov.  22, 1883) .  After  having  treated  the  materials 
with  water  they  are  heated  in  a  closed  vessel  at  a  temperature  above 
l60°  C.  and  in  the  presence  of  an  excess  of  lime,  the  amount  of  lime 
being  determined  according  to  the  quantity  of  ferrocyanides  in  the 
materials  to  be  treated.  At  first  there  is  formed  calcium  ferrocyanide 
and  calcium  sulphide,  which  latter  acts  upon  the  ferrocyanide  forming 
calcium  sulphocyanide: 


MANUFACTURE   OF  FERROCYANIDES. 

Ca2Fe(CN)6  +3CaS2  =3Ca(CNS)2  +FeS2. 

According  to  Marasse  the  decomposition  is  complete  (?) .  The  solution 
of  calcium  sulphocyanide  is  purified  and  converted  into  ferrocyanide 
by  means  of  finely  divided  iron.  The  lime  may  be  replaced  by 
potassa  or  soda. 

Holbling's  Process. — Holbling  (Ztsch.  fur  angew.  Chemie  1897) 
proposes  a  similar  method,  which  consists  in  the  conversion  of  the 
Prussian  blue  contained  in  the  purifying  materials  into  barium 
sulphocyanide  by  simply  heating  the  materials  during  several  hours 
in  the  presence  of  a  slight  excess  of  barium  sulphide  (5%),  or  only 
one-half  hour  with  a  large  excess  (10  to  15%),  and  under  a  pressure  of 
three  atmospheres.  Holbling  claims  that  the  conversion  is  complete. 
It  is  filtered  and  tjie  solution  of  barium  sulphocyanide  obtained  is 
treated  by  a  current  of  sulphurous  acid,  or  better  carbonic  acid,  in 
order  to  decompose  the  excess  of  barium  sulphide  and  to  convert  it 
into  barium  thiosulphate  and  sulphur,  or  into  barium  carbonate 
respectively,  which  being  insoluble  are  separated  by  filtration. 

Lewis'  Process.  —  The  following  process  is  recommended  by 
Lewis:  After  having  removed  the  sulphur  from  the  purifying  mate- 
rials they  are  boiled  with  milk  of  lime.  The  solution  thus  obtained, 
containing  ferrocyanide  and  sulphocyanide  of  calcium,  is  treated 
with  sulphurous  acid,  and  a  solution  of  ferrous-ferric  sulphate  which 
causes  the  formation  of  Prussian  blue.  This  is  filtered,  and  from 
the  residual  solution  the  sulphocyanides  are  removed  by  means  of  a 
copper  salt,  as  in  the  treatment  of  the  ammoniacal  liquors. 

Masco w's  Process. — The  last  process  concerning  the  treatment 
of  purifying  materials  in  order  to  remove  from  them  the  cyanogen 
compounds  to  be  mentioned  is  that  very  original  one  of  Mascow 
(French  patent  No.  301916,  1901).  Mascow  makes  use  of  the  char- 
acteristic which  ammonia  possesses  of  dissolving  the  alkali  cyanides. 
Toward  this  end  he  converts  the  cyanogen  compounds  into  alkali 
cyanides  soluble  in  ammonia,  whereas  the  other  impurities  are 
converted  into  products  insoluble  in  that  reagent.  The  materials 
are  dried  and  then  mixed  with  any  one  of  the  following  substances: 
Sodium,  magnesium,  aluminium,  iron,  zinc,  or  their  oxids,  or  car- 
bonates mixed  with  charcoal,  or  with  calcium  carbide,  or  even  with 
both  these  substances.  Either  one  or  the  other  of  these  substances  is 


:260   METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS 

used,  depending  upon  the  composition  of  the  materials.  Thus,  if 
the  materials  are  rich  in  sulphocyanides,  metallic  iron  should  be 
added  to  the  charcoal  or  to  the  potassium  carbonate  used.  The 
mixture  is  then  heated  out  of  contact  of  air,  or  in  the  presence  of 
an  inert  gas,  at  such  a  temperature  that  the  whole  of  the  cyanogen 
is  converted  into  alkali  cyanide,  which  may  then  be  dissolved  in 
.ammonia,  the  impurities  remaining  insoluble. 


CHAPTER  VIII. 
MANUFACTURE  OF  FERRICYANIDES. 

POTASSIUM  ferricyanide  (K6Fe2(CN)i2),  or  red  prussiate  of  potash 
as  it  is  more  generally  known  in  the  arts  and  in  commerce,  J£  of  suffi- 
cient importance  industrially  to  require  some  mention  relating  to 
its  preparation. 

It  is  always  obtained  by  the  oxidation  of  potassium  ferrocyanide. 

The  Chlorine  Process. — The  oldest  process,  and  one  still  in  use, 
consists  in  causing  chlorine-gas  to  act  on  potassium  ferrocyanide, 
the  reaction  being  as  follows : 

2Fe(€N)  6K4 + 2C1 = 2KC1  +  K6Fe2(CN)  12. 

This  treatment  may  be  carried  on  either  in  the  moist  or  the 
dry  way,  but  the  latter  method  is  very  rarely  used,  the  moist  method 
being  preferred.  The  operation  is  quite  difficult  to  conduct,  since 
it  requires  great  care  and  attention.  Practically  it  is  carried  on 
as  follows: 

A  solution  of  potassium  ferrocyanide  indicating  26°  B.  is  made 
in  a  copper  boiler  placed  on  a  grate.  This  solution  is  transferred 
to  a  wooden  vat,  provided  with  a  movable  cover,  into  which  a  cur- 
rent of ,  chlorine  is  conducted  until  the  addition  of  a  ferric  salt 
no  longer  produces  a  precipitate  in  the  liquor. 

The  saturation  point  is  of  extreme  importance,  for  if  too  much 
chlorine  be  used  there  is  formed  a  green  precipitate  of  complex 
composition,  to  which  the  name  of  Berlin  green  has  been  given, 
and  which  prevents  the  ferricyanide  from  crystallizing,  and  besides, 
notwithstanding  its  insolubility,  is  extremely  difficult  to  separate 
as  it  passes  through  the  niters.  On  the  other  hand,  if  too  little 
chlorine  be  used  the  ferricyanide  obtained  contains  non-decom- 
posed ferrocyanide. 

261 


262       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

Frequent  tests  are  made  by  adding  a  ferric  salt  to  a  portion 
of  the  liquor,  and  when  a  precipitate  is  no  longer  produced,  just 
at  that  point  must  the  further  addition  of  chlorine  be  stopped.  In 
order  to  tell  exactly  the  saturation  point,  the  color  of  the  solution 
should  be  examined  by  candle  light,  the  end  of  the  reaction  being 
indicated  by  the  fact  that  the  solution  being  at  first  greenish  becomes 
red.  But  this  change  in  color,  although  quite  distinct  in  dilute 
solution,  is  scarcely  perceptible  in  concentrated  solution.  The 
testing  should  preferably  be  done  with  a  ferric  salt  absolutely  free 
from  ferrous  salts. 

Stirring  must  be  kept  up  continually  during  the  addition  of  chlo- 
rine, otherwise  the  ferricyanide  formed  at  certain  points  would  be 
broken  up  under  the  prolonged  action  of  chlorine,  which  would  pro- 
duce the  above-mentioned  green  compound. 

When  the  addition  of  chlorine  is  stopped,  the  solution  is  filtered 
and  immediately  transferred  to  a  copper  boiler  similar  to  that  in 
which  the  ferrocyanide  was  dissolved,  and  concentrated  to  27-28°  B. 
by  continued  boiling,  for  the  crystals  have  a  tendency  to  become 
deposited  on  the  sides  of  the  vat.  When  this  point  is  reached  the 
liquor  is  transferred  to  wooden  vats  or  crystallizing  vessels,  where 
it  is  allowed  to  stand  for  five  days.  At  the  end  of  this  tune  the 
mother-liquors  are  separated  from  the  red  prussiate  crystals  by 
decantation.  These  mother-liquors  are  subjected  either  to  two 
further  concentrations,  to  28  to  29°  B.,  or  else  they  may  be  used 
in  dissolving  a  fresh  quantity  of  yellow  prussiate  which  is  to  be 
subjected  to  the  action  of  chlorine.  When  the  conversion  is  com- 
plete the  solution  of  ferricyanide  is  concentrated  to  29°  B.  and  left 
to  crystallize.  These  new  mother-liquors  which  are  decanted  are 
concentrated  until  they  register  31°  B.  while  hot;  after  which  they 
are  transferred  into  vats  where  the  potassium  chloride  is  precipitated. 
After  standing  six  or  seven  hours,  the  liquors  while  still  warm  are 
decanted,  and  may  again  be  used  to  dissolve  ferrocyanide.  The 
crude  crystals  of  the  four  operations  are  then  collected  and  dissolved 
in  hot  water  in  a  copper  boiler;  the  solution  is  concentrated  to  27° 
B.  while  hot,  and  then  transferred  into  wooden  vats  or  crystallizing 
vessels,  where  they  are  left  for  several  days. 

As  large  crystals  are  commercially  much  more  important,  in  order 
to  obtain  a  beautiful  crystallization,  it  is  advisable  to  pour  gently  on 


MANUFACTURE  OF  FERRICYANIDES.  263 

the  surface  of  the  solution  about  20  litres  of  water,  which  floating  on 
the  surface  prevents  the  formation  of  small  crystals.  When  the 
crystallization  is  complete  the  mother-liquors  are  decanted,  and 
may  be  used  in  dissolving  a  fresh  quantity  of  crude  crystals.  They 
may  thus  be  used  five  or  six  times  provided  they  are  not  too  heavily 
charged  with  potassium  chloride.  When  this  salt  becomes  too 
abundant  the  mother-liquors  are  concentrated  in  order  to  remove 
it  by  crystallization,  and  it  is  then  sold  as  fertilizer. 

The  crystals  of  potassium  ferricyanide  are  allowed  to  drain  and 
then  are  dried  upon  flat  iron  plates  gently  warmed  with  waste  heat. 
This  treatment  should  preferably  be  conducted  in  a  dark  place,  and 
be  done  as  rapidly  as  possible  in  order  to  avoid  too  long  contact  with 
air. 

In  this  way  for  100  parts  of  yellow  prussiate  about  70  parts  of 
ferricyanide  are  obtained,  the  theoretical  yield  being  77.9. 

The  process  by  the  dry  way  consists  in  causing  chlorine  to  act  upon 
powdered  ferrocyanide,  placed  in  very  thin  layers  in  revolving 
apparatus  or  in  chambers  similar  to  those  used  in  the  manufacture  of 
chloride  of  lime. 

The  ferrocyanide  is  first  deprived  of  part  of  its  water  of  crys- 
tallization in  order  that  it  may  be  powdered,  as  chlorine  exerts 
but  a  slight  action  on  the  anhydrous  salt;  then  it  is  ground  with  a 
grindstone,  sifted,  and  subjected  to  the  action  of  chlorine  till  ab- 
sorption no  longer  takes  place.  The  reaction  is  exactly  the  same 
as  in  the  moist  way:  Ferricyanide  and  potassium  chloride  are 
formed  which  may  be  separated  by  crystallization.  Quite  often 
the  product  obtained  in  the  dry  way  is  sold  just  as  it  is  when 
removed  from  the  absorption  apparatus,  i.e.,  in  the  form  of  a 
powder  consisting  of  a  mixture  of  ferricyanide  and  chloride  of 
potassium.  Various  other  methods  have  been  devised  for  the  pro- 
duction of  red  prussiate. 

Reichardt's  Process.— Reichardt  (1869)  proposed  replacing  chlo- 
rine by  bromine,  while  Kramer  recommended  digesting  Prussian  blue 
with  potassium  hypochlorite.  Rodgers  advised  precipitating  a 
solution  of  a  mixture  of  2  parts  potassium  sulphate  and  1  part  iron 
alum  with  barium  cyanide,  then  to  filter,  concentrate,  and  crystallize. 
It  is  not  known  that  these  methods  have  been  tried  on  an  industrial 
scale. 


264      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

The  action  of  ozone  or  of  ozonized  oxygen  has  likewise  been 
tried,  the  ferrocyanide  being  very  rapidly  converted  into  ferri- 
eyanide. 

Electricity  produces  the  same  result.  Two  methods  have  been 
invented  with  a  view  to  utilizing  the  electric  current  on  ferrocyanide. 
These  are  the  processes  of  the  Societe  des  Mines  at  Bouxvillers,  and 
of  Dubosc. 

It  is  well  known  that  under  the  action  of  the  electric  current 
passing  through  an  aqueous  solution  of  ferrocyanide,  the  latter  is 
converted  into  ferricyanide  which  appears  at  the  positive  pole, 
while  at  the  negative  pole  potassium  is  deposited,  which,  in  contact 
with  water,  forms  hydrogen  and  potassa, 


2Fe(CN)  6K4  =Fe2(CN)  i2K6  +  K2, 

but  it  is  likewise  known  that  the  action  is  reversible,  the  electric 
current  converting  ferricyanide  into  ferrocyanide.  This  phenomenon 
is  explained  by  supposing  that  in  the  first  case  the  ferricyanide  is 
reduced  by  the  hydrogen  produced  at  the  negative  pole,  while  in  the 
second  case,  the  oxygen  of  the.  positive  pole  oxidizes  the  ferro- 
cyanide. On  the  other  hand,  the  prolonged  action  of  the  potassa 
converts  a  part  of  the  ferricyanide  into  ferrocyanide. 

Process  of  the  Mines  at  Bouxvillers.  —  This  process  (French  patent 
No.  176675,  Oct.  15,  1886)  aims  at  avoiding  these  very  objections. 
The  conditions  under  which  the  electric  current  should  be  conducted 
have  been  so  carefully  studied  that  there  is  no  formation  of  Prussian 
blue,  and  the  ferricyanide  formed  is  not  decomposed.  The  electrodes 
,are  placed  in  cells  separated  by  porous  diaphragms,  the  negative 
cell  containing  water,  the  positive  cell  being  filled  with  a  solution  of 
potassium  ferrocyanide. 

If  under  these  conditions  an  electric  current  of  an  electromotive 
force  of  1.4  to  5.4  volts  be  conducted  the  ferrocyanide  is  converted 
into  ferricyanide  which  is  formed  in  the  positive  cell,  whereas  in  the 
negative  cell  caustic  potash  is  formed  with  the  liberation  of  hydrogen. 
In  this  way  the  two  solutions  are  separate,  and  the  potash  does  not 
exert  its  injurious  action  on  the  ferricyanide,  and  thus  a  pure  solution 
of  ferricyanide  is  obtained,  and  it  remains  only  to  concentrate  and 
to  crystallize  it. 


MANUFACTURE  OF  FERRICYANIDES.  265 

The  water  of  the  negative  cell  may  be  replaced  by  mercury,  in 
which  case  an  amalgam  of  mercury  and  potassium  is  formed. 

Dubosc's  Process.— Dubosc  (French  patent  No.  207193,  July,  24, 
1890)  likewise  uses  the  electric  current  in  order  to  convert  the  ferro- 
cyanide into  the  ferricyanide.  The  electrolysis  takes  place  in  the 
presence  of  sodium  chloride.  At  the  same  time,  or  afterwards,  a 
current  of  carbonic  acid  is  passed  through,  which  neutralizes  the 
alkaline  base  and  separates  the  ferricyanide  formed  from  the  car- 
bonate and  the  chloride: 

2K4Fe(CN)  6  +  02  +  2C02 = 2C03K2  +  K6Fe2(CN)  12. 

The    Process  of    the    Deutsche    Gold   und   Silber   Scheide-Anstalt 

(French  patent  No.  218246,  1891)  has  for  its  object  the  avoiding 
of  the,  formation  of  soluble  salts,  which  remaining  in  the  solution 
together  with  the  ferricyanide  contaminate  the  latter,  which  often 
requires  purification  more  or  or  less  costly. 

It  consists  in  using  an  alkaline-earth  ferrocyanide,  which  after 
oxidation  only  leaves  an  insoluble  compound.  The  oxidation  is 
made  more  easily,  it  seems,  and  either  the  electric  current  or  per- 
manganate or  any  other  oxidizing  agent  which  does  not  leave  behind 
any  soluble  compound  may  be  used.  In  any  case,  the  small  amount 
of  alkaline-earth  base  which  dissolves  may  be  precipitated  either 
by  sulphuric  or  carbonic  acid. 

Calcium  ferrocyanide  is  preferred,  in  which  case,  when  perman- 
ganate is  used  as  the  oxidizing  agent,  the  reaction  is  as  follows: 

3Ca2Fe(CN)6  +  7K4Fe(CN)6+2KMn04 

=  10K3Fe(CN)6 +2MnO +6Ca(X 

The  oxid  of  manganese  and  the  greater  part  of  the  lime,  being 
insoluble,  remain  in  suspension.  By  passing  a  current  of  carbonic 
acid,  the  small  amount  of  dissolved  lime  is  easily  precipitated.  After 
filtration  an  absolutely  pure  solution  of  ferricyanide  is  obtained,, 
which  may  be  concentrated  and  crystallized. 

The  process  may  likewise  be  applied  to  the  chlorine  method, 
the  oxidation  being  more  rapid  and  the  yield  greater  than  by  the 
ordinary  method.  But  this  oxidizing  agent  leaving  behind  soluble 
compounds,  pure  solutions  are  not  obtained,  as  is  the  case  where 
the  oxidizing  agent  leaves  behind  only  insoluble  impurities  which 
may  be  easily  fierlted  off. 


266       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS 

Kassner's  Process. — This  process  (1893)  is  based  on  a  reaction 
which  was  pointed  out  by  Lunge  in  1881.  This  investigator  recom- 
mends the  oxidation  of  ferrocyanide  by  means  of  lead  peroxid 
and  carbonic  acid  according  to  the  reaction 

2FeK4(CN)6  +  0  +  H20 = Fe2K6(CN)  12 + 2KOH. 

Kassner,  however,  no  longer  uses  peroxid  of  lead,  but  instead 
an  alkaline-earth  plumbate,  e.g.  calcium  plumbate.  This  sub- 
stance, the  formula  of  which  is  Ca2Pb04  or,  better,  CaO,Pb02;  pos- 
sesses the  peculiar  property  when  in  contact  with  even  the  weak- 
est acids,  such  as  carbonic  acid  and  even  carbonates  and  some  other 
salts,  of  becoming  converted  into  lead  bioxid  and  the  calcium 
salt  of  the  acid  used.  Thus  if  calcium  plumbate  be  heated  with 
sodium  carbonate  at  130°  under  pressure,  an  insoluble  mixture  of 
chalk  and  lead  bioxid  is  obtained,  caustic  soda  being  in  solution: 

Ca2Pb04 + 2C03Na2 + 2H20 = Pb02 + 2C03Ca + 4NaOH. 

Now  then,  if  a  mixture  of  chalk  and  lead  bioxid  be  held  in  sus- 
pension in  a  solution  of  potassium  ferrocyanide  and  a  current  of 
carbonic  acid  be  conducted  through  it,  there  will  be  formed  potassium 
ferricyanide,  lead  oxid,  carbonates  of  lime  and  of  potash,  accord- 
ing to  the  reaction 

2FeK4(CN)6 +Pb02 +2C03Ca +C02 

=  Fe2K6(CN)i2 +PbO + 2C03Ca +C03K2. 

By  adding  to  the  solution  calcium  ferricyanide,  the  carbonate  of 
potash  is  converted  into  carbonate  of  lime,  so  that  nothing  remains 
in  solution  except  potassium  ferricyanide,  which  may  be  separated 
by  filtration,  concentration,  and  crystallization: 

3Fe2(CN)i2K6+3C03K2+Fe2(CN)12Ca3=4Fe2(CN)12K6+3C03Ca. 

It  is  best  to  add  the  calcium  ferricyanide  after  the  oxidation 
with  the  lead  salt,  for  the  chalk  formed  in  this  second  reaction  may 
thus  be  collected,  and  so  not  hinder  the  recovery  of  the  lead  salt. 

Calcium  ferricyanide  is  obtained  by  the  action  of  calcium  plum- 
bate  on  the  corresponding  ferrocyanide.  A  very  intimate  mixture  of 


MANUFACTURE  OF  FERRICYANIDES.  267 

lead  peroxid  and  chalk  is  thus  made,  and  with  a  slight  excess  of 
this  oxidizing  mixture  calcium  f  errocyanide  in  concentrated  solution, 
under  pressure,  is  oxidized.  The  solution  of  calcium  ferricyanide 
obtained  may  be  directly  utilized  in  the  conversion  of  alkali  car- 
bonate. 

Carl  Beck's  Processes.  —  These  processes  (German  patent  No.  15459, 
Nov.  28,  1893;  No.  16088,  May  4,  1894;  No.  17677,  May  22,  1895) 
are  based  on  the  action  of  persulphates,  which  are  very  energetic 
oxidizing  agents,  as  is  well  known.  The  reaction  is  as  follows: 


Either  the  persulphate  of  ammonia  or  that  of  sodium  may  be 
used,  but  on  account  of  the  greater  solubility  of  the  former,  it  -is 
preferred.  A  solution  of  potassium  ferrocyanide  is  prepared  by 
dissolving  this  salt  in  exactly  its  weight  of  hot  water.  When  this 
solution  has  cooled  to  60°,  a  solution  of  ammonium  persulphate 
containing  540  grams  of  this  salt  per  liter  of  water  is  slowly  added. 
The  reaction  being  very  lively,  heat  is  liberated  to  such  an  extent 
as  to  necessitate  cooling  the  vessel  in  which  the  reaction  is  con- 
ducted. The  neutral  double  sulphate  of  ammonium  and  potash, 
being  but  slightly  soluble,  is  deposited  on  cooling.  It  is  separated 
by  decantation;  the  ferricyanide  is  then  crystallized.  On  account 
of  the  relatively  high  cost  of  persulphates  it  seems  improbable  that 
this  process  should  be  used  on  a  large  scale. 

Williamson's  Process.  —  One  process  which  has  been  somewhat 
.spoken  about  lately  and  which  had  already  been  pointed  out  by 
Williamson,  still  remains  to  be  mentioned.  It  consists  in  starting 
with  the  product  known  as  soluble  Prussian  blue,  a  product  which 
is  obtained  by  pricipitating  iron  sesquioxid  with  an  excess  of  potas- 
sium ferrocyanide.  The  precipitate  obtained  is  washed,  the  wash- 
water  rapidly  becoming  blue,  due  to  the  presence  of  the  compound 
[Fe(CN)6]2Fe2K2,  or  ferric  potassium  ferrocyanide.  When  this  prod- 
uct is  treated  with  potassium  ferrocyanide,  it  yields  potassium  ferri- 
cyanide and  ferrous  potassic  ferrocyanide, 

[Fe(CN)6]2Fe2K2+2K4Fe(CN)6=Fe2K(CN)i2+2Fe6(CN)6FeK2. 

ferric  potassic  ferro-  ferrous  potassic 

cyanide.  ferrocyanide 


268      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

It  is  only  necessary  to  digest  the  potassium  ferrocyanide  with  a 
slight  excess  of  potassium  ferri-ferrocyanide,  then  to  filter,  evaporate, 
and  allow  to  crystallize.  The  ferricyanidethus  obtained  is  perfectly 
pure,  and,  as  may  be  seen,  the  process  requires  neither  great  care 
nor  complicated  apparatus.  There  remains  on  the  filter  a  mixture 
of  potassium  ferro-ferrocyanide  and  the  excess  of  potassium  ferri- 
ferrocyanide  used.  This  latter  product  may  be  recovered  and  may 
again  be  used  in  the  manufacture  of  a  fresh  amount  of  ferricyanide 
by  treating  it  with  nitric  acid.  The  same  amount  of  this  product 
could  thus  be  used  indefinitely. 

Notwithstanding  its  extreme  simplicity  we  do  not  know  if  this 
process  has  been  used  industrially. 


CHAPTER  IX. 
MANUFACTURE  OF  SULPHOCYANIDES. 

SULPHOCYANIDES,  sulphocyanates,  or  rhodanates  as  they  are  some- 
times called,  are  very  little  used  in  the  arts.  Yet,  at  one  time  they 
were  very  important  industrially,  for  they  were  considered  a  very 
profitable  source  of  manufacture  as  an  intermediary  product  of 
cyanides.  -  On  this  account  their  production  was  the  basis  of  several 
processes  about  which  the  investigator  and  manufacturer  should 
know.  These  processes,  especially  two  of  them,  mark  a  real  progress 
in  the  cyanide  industry,  and  they  will  be  minutely  described  as  they 
deserve. 

Before  entering  upon  the  study  of  the  various  methods  for  the 
manufacture  of  sulphocyanides,  it  will  be  well  to  briefly  recall 
the  different  methods  of  obtaining  these  compounds. 

Sulphocyanides  may  be  produced: 

(1)  By  the  direct  action  of  sulphur  on  a  cyanide, 

CNK  +  S=CNSK, 

or  on  a  f  errocyanide,  either  by  boiling  or  by  ignition. 

(2)  By  igniting  nitrogenous  substances  with  potassium  sulphate, 
or  with  sulphur  and  potassium  carbonate. 

(3)  By  the  action  of  cyanogen,  hydrocyanic  acid,  or  cyanides  on 
metallic  sulphides, 

2CN  +  K2S  =  CNK + CNSK, 

or  by  the  action  of  hydrocyanic  acid  on  a  mixture  of   ammonia, 
sulphur,  and  ammonium  sulphide. 

(4)  By  the  action  of  carbon  bisulphide  on  ammonia  on  heating: 

CS2 +4NH3  =  (NH4)2S +CNS(NH4). 

269, 


270       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

(5)  By  the  action  of  heat,  or  of  alkalis  on  thiosulphocarbamates: 

CS\SK  2  +  2KOH 


(6)  By  the  'action  of  heat  on  ammonium  thiocarbamate  (Berthelot, 
Bull,  de  la  Soc.  chim.  de  Paris,  1868)  : 

CO\SNH24+heat  =H2°  +CNS(NH4). 

(7)  By  the  decomposition  of  fulminates  by  the  aid  of  hydrogen 
sulphide: 

(C2N202)2Hg2  +4H2S  =2HgS  +2C02  +2CNS(NH4). 

(8)  By  the  action  of  water  and  heat  on  Thio-urea: 

CS(NH2)2=CNS(NH4). 

(9)  By  the  action  of  hot  sulphuric  acid  on  nitrogenous  organic 
•substances. 

Of  all  these  methods  of  preparation  there  is  one  which  should  be 
especially  retained  in  mind,  for  it  forms  the  basis  of  the  methods  of 
production  of  sulphocyanides  on  an  industrial  scale.  That  is  the 
one  which  depends  on  the  action  of  carbon  bisulphide  on  ammonia. 

Gelis'  Process.  —  To  Gelis,  a  Frenchman,  belongs  the  honor  of 
having  applied  this  reaction  to  an  industrial  process. 

This  process  is  already  old  (1860),  and  it  was  put  in  operation  for 
the  first  time  in  the  inventor's  own  works  at  Villeneuve-la-Garenne. 

It  was  carried  on  as  follows,  the  operation  comprising  two  distinct 
stages. 

(1)  The  action  of  sulphide  of  carbon  on  ammonium  sulphide, 
with  formation  of  ammonium  sulphocarbonate  : 

CS2+2(NH4HS)  =CS3(NH4)2  +  H2S. 

(2)  Conversion  of  ammonium  sulphocarbonate  into  ammonium 
.sulphocyanide  by  heating  it  to  100°  with  potassium  sulphide 

2CS3(NH4)  2  +  K2S  =  2CNSK  +  2NH4HS  +  3H2S. 


MANUFACTURE  OF  SULPHOCYANIDES.  271 

The  first  stage  takes  place  in  an  apparatus  fitted  up  with  a  wide- 
bladed  stirrer.  The  sulphocarbonate  formed  is  transferred  to  a 
sheet-iron  still  together  with  potassium  sulphide  and  the  mixture 
is  heated  to  100°.  The  hydrogen  sulphide  and  the  ammonium 
sulphydrate  set  free  are  condensed  in  a  sheet-iron  cylinder  entirely 
surrounded  with  water,  into  which  gaseous  ammonia  produced  in 
another  boiler  is  conducted,  which  is  used  in  absorbing  the  hydrogen 
sulphide  in  order  to  form  ammonium  sulphydrate,  which,  together 
with  that  produced  in  the  decomposition  of  ammonium  sulpho- 
carbonate, is  used  in  the  manufacture.  The  condensation  ends  in 
a  coil  in  sheet-iron  boxes  fixed  up  with  compartments,  and  finally 
in  bottles. 

The  sulphocyanide  was  then  treated  at  140-160°  with  reduced 
iron  in  deep  wide  pans  made  of  cast  iron  and  hermetically  sealed. 

In  his  report  to  the  Imperial  Commission  of  the  Exposition  at 
London  in  1862,  Gelis  mentions  the  fact  that  his  experiments  have 
been  carried  on  with  more  than  1000  kg.  at  one  time,  and  that  the 
raw  materials  are  products  easily  found  in  the  market.  He  adds  that 
the  manufacture  is  extremely  easy 

In  the  "  Annales  des  Mines  du  Conservatoire  des  Arts  et  Metiers,  " 
1862,  page  55,  Payen  gives  the  net  cost  of  ferrocyanide  manufactured 
by  Gelis'  process,  the  cost  being  based  on  the  production  of  30,000  kg. 
potassium  ferrocyanide. 

Carbon  bisulphide  (crude) 35,000  kg.  @  45  fcs.  per  100  kg 15,750  fcs. 

Potassium  sulphate 36,400  "   "    40    "     "        "       14,510  " 

Ammonium  sulphate 25,300"   "    35  "     "        "      8,875" 

Reduced  iron 50,000  ""    10    "     "        "      5,000" 

Quicklime 17,500""      4"     "        "      700" 

Cost  of  converting  the  potassium  sulphate  into  potassium  sulphide,  3  fcs. 

per  100  kg. . 1,092  " 

Labor,  12  men  @  3.50  fcs.  per  day,  30  days 1,260  " 

Fuel 600  " 

Hent  and  general  expenses  for  one  month 1,000  ' ' 

Losses  of  raw  materials,  etc.,  15%  of  expenses 7,322  ' ' 


56,139  fcs. 
Deducting  from  the  above  one  third  of  the  potash  in  the 

form  of  carbonate 5,000  fcs. 

25,000  kg.  sulphur  @  13  fcs 3,250  " 

8,250  fcs. 


Net  cost  for  30,000  kg.  potassium  ferrocyanide 47,889  fcs. 

or  1.59  fcs.  per  kilogram. 


272       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS 

GehV  process  had  but  a  short  existence,  as  to-day  it  is  entirely 
abandoned,  because  it  is,  in  fact,  rather  difficult  to  operate  it  on  a 
large  scale.  Besides,  it  should  be  remarked  that  only  half  of  the  am- 
monium sulphocarbonate  is  converted  into  potassium  sulphocyanide 
at  the  time  of  the  action  of  potassium  sulphide,  and,  moreover,  it 
requires  costly  and  complicated  apparatus. 

Gelis7  method  was  again  taken  up  about  1878  by  two  manufac- 
turers, A.  de  Gunzburg  and  Tcherniac  (French  patents  of  Feb.  12, 
1878,  April  25,  1879,  Dec.  24,  1880),  who  improved  it  remarkably. 
The  process  is  as  follows : 

(1)  Production  of  thiosulphocarbamate  of  ammonia  by  the  direct 
union  of  carbon  bisulphide  and  ammonia  at  100°  under  pressure: 

CS2 + 2NH3  =  NH2— CS— SNH4. 

(2)  Conversion  of  this  salt  into  ammonium  sulphocyanate  by 
heating  at  105°: 

NH2— CS— SH4N  =  NCS— NH4 + H2S. 

(3)  The   conversion   of    ammonium  sulphocyanate  into  calcium 
sulphocyanate  by  distillation  with  quicklime,  and  the  reproduction 
of  half  of  the  ammonia  used  in  the  reaction : 

2NCS  •  NH4  +  Ca(OH)  2  =  (NCS)  2Ca + 2NH3  +  H20. 

(4)  The   conversion   of   calcium   sulphocyanate   into   potassium 
sulphocyanate  by  treating  it  with  potassium  sulphate : 

(NSC)  2Ca  +  S04K2  =  S04Ca + 2CNSK. 

(5)  Conversion  of  the  potassium  sulphocyanide  into  potassium 
ferrocyanide  with  iron  at  450°  according  to  the  reactions  which  we 
have  already  pointed  out : 

CNSK + Fe  =  FeS  +  CNK , 
FeS  +  6CNK  *  Fe(CN)6K4  +  K2S. 


MANUFACTURE  OF  SULPHOCYANIDES.  273 

(The  object  of  Tcherniac's  process  was  the  -production  of  potassium 
ferrocyanide.) 

As  may  be  seen,  the  whole  of  these  reactions  forms  a  really  com- 
plicated work,  and  difficult  enough  to  carry  on  an  industrial  scale, 
although  theoretically  it  appears  quite  simple.  And  it  is  only  by 
reason  of  unheard-of  efforts,  of  rare  perseverance,  and  of  long  and 
patient  investigations,  which  are  all  to  the  honor  of  Tcherniac  and 
de  Giinzburg,  that  these  two  learned  manufacturers  succeeded  in 
exploiting  their  process  on  a  large  scale. 

The  Campagnie  Generate  des  Cyanures,  which  is  exploiting  the 
patents  of  Tcherniac  and  de  Giinzburg,  operates  in  the  following 
way  in  its  works  at  St.  Denis,  the  complete  manufacture  comprising 
five  operations: 

(1)  Preparation  of  ammonium  thiosulphocarbamate. 

(2)  Preparation  of  ammonium  sulphocyanate. 

(3)  Preparation  of  calcium  sulphocyanate. 

(4)  Preparation  of  potassium  sulphocyanate. 

(5)  Preparation  of  potassium  ferrocyanide. 

(1)  Preparation  of  Ammonium  Thiosulphocarbonates. — As  has  been 
seen,  this  product,  results  from  the  action  of  carbon  bisulphide  on 
ammonia.  The  operation  is  carried  on  in  a  series  of  small  auto- 
claves, forged  iron  boilers,  tested  to  a  very  high  pressure,  and  her- 
metically covered. 

Each  one  of  these  autoclaves  is  provided  with  a  thermometer,  a 
manometer,  a  wide-bladed  stirrer,  and  three  tubulatures  or  cocks, 
one  for  the  inlet  of  the  solutions,  the  other  for  the  exit  of  the  gases 
which  are  produced,  and  the  third  for  emptying  the  apparatus. 
They  are  encased  in  an  exterior  wrapper  heated  with  steam.  The 
reaction  is  conducted  separately  in  each  one  of  the  autoclaves  repre- 
sented in  Fig.  22.  A  pump  p  feeds  the  autoclaves  with  a  mixture 
of  carbon  bisulphide,  20%  ammonia,  and  ammoniacal  liquors  fur- 
nished by  preceding  operations. 

When  the  apparatus  has  been  suitably  charged  with  this  mixture 
the  cock  connecting  with  the  pump  is  closed,  and  the  stirrer  is  set 
in  motion.  Steam  is  admitted  through  the  tube,  V,  and  the  whole 
heated  till  the  thermometer  registers  100°.  At  this  moment  the 
inlet  of  steam  is  stopped,  and  the  stirrer  is  kept  going  till  the  pressure 
in  the  autoclave  is  15  atmospheres;  the  operation  may  then  be. 


274       METHODS   OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

considered  finished.  The  product  of  the  reaction  is  a  mixture  of 
ammonium  sulphocarbonate,  and  carbon  bisulphide  in  excess.  The 
cock  of  the  compressing  tube,  C,  plunging  to  the  bottom  of  the 
apparatus  is  opened,  and  owing  to  the  effects  of  the  high  pressure 
in  the  autoclave,  the  mixture  is  violently  driven  into  the  still,  A, 


FIG.  22. 

represented  in  Fig.  23,  and  in  which  the  conversion  of  ammonium 
sulphocyanate  takes  place. 

(2)  Separation  of  Ammonium  Sulphocyanate. — The  still  in  which 
this  precipitation  is  carried  on  consists  of  an  ordinary  boiler,  heated 
to  a  temperature  of  105-110°  C.  by  means  of  a  coil  of  steam 
placed  at  the  bottom.  Under  these  conditions  the  thiosulphocar- 
bonate  is  decomposed  in  ammonium  sulphocyanate  and  hydrogen 


MANUFACTURE  OF  SULPHOCYANIDES. 


275 


sulphide,  while  the  remaining  carbon  bisulphide  and  ammonia  distill. 
The  still  is  surmounted  with  a  cylindrical  vessel,  B}  called  an  en- 
trainment  device,  the  object  of  which  is  to  separate  the  gaseous 
products  from  the  liquid  products  mechanically  drawn  over  during 
the  distillation.  These  latter  come  with  the  gaseous  products 
through  the  tube,  &,  into  the  entrainment  device,  there  they  are 
condensed  and  returned  to  the  still,  A,  through  the  tube,  c,  which 
plunges  into  the  liquid  to  be  distilled,  while  the  gaseous  products 
continue  their  course  to  the  absorption  apparatus. 

This  apparatus  consists  of  two  columns  filled  with  pieces  of  coke, 
placed  above  a  surface  heat-exchanger,  which  is  itself  built  upon  a 
very  large  receiver,  into  which  the  products  of  condensation  are  col- 


FIG.  23. 

lected.  A  gasometer  bell,  whose  capacity  is  about  15  cu.  m.,  is  used 
as  a  regulator,  and  at  the  same  time  holds  back  the  residual  gases 
of  the  condensation,  consisting  almost  entirely  of  hydrogen  sulphide. 
The  gases  which  emerge  from  the  entrainment  device  and  which 
consist  of  a  complicated  mixture  of  hydrogen  sulphide,  ammonium 
sulphide  (obtained  from  the  action  of  hydrogen  sulphide  on  ammonia 
in  excess),  water-vapor,  and  carbon  bisulphide,  pass  into  the  coke 
column,  C,  then  into  the  exchanger,  E,  and  are  condensed  in  the 


'276       METHODS   OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

vessel;  R.  A  pump,  P,  takes  this  liquid  and  transfers  it  through  the 
tube,  /,  to  the  upper  part  of  the  coke  column,  where  it  is  discharged 
in  the  form  of  a  continuous  shower  which,  while  making  sure  of  a 
complete  condensation,  prevents  any  stoppage  which  the  deposits 
of  ammonium  sulphide  might  occasion. 

The  second  column,  C'-D',  is  used  as  a  reflux  condenser,  and 
allows  the  last  portions  of  the  liquid,  which  might  have  escaped 
treatment  to  be  collected. 

Carried  out  in  this  way,  the  condensation  is  very  imperfect;  in 
fact,  notwithstanding  all  the  desirable  improvements  of  the  condensa- 
tion apparatus,  hydrogen  sulphide  always  carries  along  an  appre- 
ciable amount  of  carbon  bisulphide,  sometimes  even  20%  of  the 
product  used.  Notwithstanding  this,  the  inventors  of  this  process 
have  succeeded  in  preventing  completely  the  disastrous  effects  of 
this  contamination  by  making  the  hydrogen  sulphide  bubble  through 
oil,  preferably  heavy  petroleum  oil.  Under  these  conditions  the 
carbon  bisulphide  only  is  absorbed  by  the  oil,  and  it  only  requires  a 
distillation  to  separate  it  and  to  revivify  the  oil,  whereas  the  hydrogen 
sulphide  escapes  in  an  almost  pure  state.  (Patent  of  May  31,  1881.) 
Thus  carried  on,  this  treatment,  which  is  one  of  the  finest  examples 
of  continuous  operations,  gives  a  large  yield  which  may  even  reach 
95%  of  the  theoretical. 

The  ammonium  sulphocyanate  remaining  in  the  still  is  dis- 
charged after  the  distillation  through  the  cock  d. 

These  first  two  operations  of  Tcherniac  and  de  Giinzburg's  process 
require  very  strong  apparatus.  With  the  exception  of  the  coil  in 
the  still,  which  is  of  tin  or  of  aluminum,  the  apparatus  should  be 
of  forged  or  of  cast  iron,  which  metals  are  known  through  experi- 
ence to  be  the  most  suitable  for  this  kind  of  work,  in  fact,  in  the 
presence  of  a  slight  excess  of  ammonium  sulphydrate,  iron  is  suffi- 
ciently resistent.  On  the  other  hand,  it  is  absolutely  necessary 
that  the  coil  should  be  of  tin  or  of  aluminum,  for  in  this  part  of 
the  apparatus  the  iron,  no  longer  protected  by  the  ammonium  sul- 
phide, would  be  attacked  by  a  small  quantity  of  free  sulphocyanic 
acid,  produced  by  the  partial  dissociation  of  ammonium  sulpho- 
cyanide,  ferrous  sulphocyanate  being  formed  which  would  con- 
taminate the  product  and  color  it  red;  tin  is  but  slightly  attacked, 
and  pure  aluminum  not  at  all. 


MANUFACTURE  OF  SULPHOCYANIDES.  277 

If  absolutely  pure  ammonium  sulphocyanide  is  desired  it  will 
be  necessary  to  carry  on  the  operation  in  an  aluminum  apparatus. 
A  still  entirely  of  aluminum  has  been  constructed,  and  the  results 
obtained  have  been  in  all  points  entirely  satisfactory. 

At  present  a  great  deal  of  ammonium  sulphocyanide  is  used 
in  the  preparation  of  aluminum  mordants  in  dyeing,  and  the  salts 
to  be  used  for  this  purpose  should  be  especially  free  from  iron. 
In  this  case  the  manufacture  is  carried  on  in  aluminum  apparatus, 
and  it  is  stopped  at  this  point;  the  ammonium  sulphocyanide 
which  remains  in  the  still  is  cleared  out,  evaporated  at  the  tem- 
perature of  125°,  and  then  allowed  to  crystallize  in  wooden  vats 
lined  with  tin. 

When  the  operation  has  been  carried  on  in  an  iron  still  and  the 
ammonium  sulphocyanide  thus  obtained  therefore  contains  ferrous 
sulphocyanide,  which,  in  contact  with  atmospheric  oxygen,  is  con- 
verted into  ferric  sulphocyanate  and  gives  the  characteristic  red 
color  of  this  latter  salt,  it  is  necessary,  if  it  is  desired  to  obtain  a 
white  salt  capable  of  remaining  white,  to  precipitate  the  ferrous 
salt  with  ammonium  sulphydrate  or  simply  to  subject  the  solu- 
tion, to  which  a  little  ammonia  has  been  added,  to  the  action  of 
a  current  of  air,  which  precipitates  the  whole  of  the  iron  as  peroxide. 
This  is  allowed  to  stand  and  then  filtered  and  the  solution  evapo- 
rated in  a  tin  boiler. 

If,  on  the  other  hand,  the  object  is  to  manufacture  potassium 
ferrocyanide  the  operations  which  have  been  previously  described 
are  continued. 

(3)  Preparation  of  Calcium  Sulphocyanate. — This  is  based  on' 
the  following  reaction: 

2CNS  •  NH4 + CaO  =  (CNS)  2Ca^+ 2NH3 + H20. 

The  apparatus  which  is  used  for  this  treatment  consists  of  a 
vertical  boiler;  or  still  (Fig.  24)  heated  by  means  of  the  steam  coil,  V. 
This  coil  surrounds  a  perforated  sheet-iron  basket  in  which  lime 
is  placed.  Besides,  this  still  or  reservoir  is  provided  with  a  ther- 
mometer and  a  diverter  similar  to  that  of  the  still  just  described. 
The  lime  having  been  placed  in  the  basket  the  reservoir  is  charged 
with  the  solution  of  ammonium  sulphocyanide,  and  the  tempera- 
ture raised  to  125°.  Under  these  conditions  the  reaction  indi- 


278   METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

cated  above  is  brought  about  and  the  ammonia  set  free  is  dis- 
tilled. When  no  more  ammonia  distils  over  the  reaction  is  con- 
sidered finished,  calcium  sulphocyanate  remaining  in  the  reservoir. 
The  ammonia  distilled  over  is  condensed  in  the  following  apparatus: 
On  emerging  from  the  still  the  ammonia  passes  into  the  diverter, 
whose  object  it  is  to  separate  the  liquids  from  the  vapors;  a  separa- 
tion which  is  rather  delicate,  owing  to  the  abundant  froth  produced 
by  the  solution  of  calcium  sulphocyanate,  but  which  is  easily  enough 
done  in  the  entrainment  device  where  the  foam  liquefies  and  flows 
back  into  the  reservoir,  whereas  the  ammonia  continues  its  course 
reaching  the  exchanger,  C,  where  it  is  partly  condensed.  The  last 


FIG.  24. 

portions  are  held  back  in  the  absorber,  D,  cooled  by  a  coil  contain- 
ing cold  water.  The  amount  of  water  which  flows  is  so  regulated 
that  a  20%  solution  of  ammonia  is  obtained,  which  may  be  used 
in  the  manufacture  of  ammonium  thiosulphocarbonate. 

The  solution  of  calcium  sulphocyanate  which  remains  in  the 
distill  ing-reservoir  is  removed  through  the  cock,  C,  and  then  treated 
so  as  to  convert  it  into  potassium  sulphocyanide. 

Conversion  of  Ammonium  Sulphocyanate  into  Potassium  Sulpho- 
cyanate.— This  operation  takes  place  in  open  cylindrical  boilers 
heated  directly  by  fire  and  fitted  up  with  scraper-stirrers.  First, 
a  concentrated  and  boiling  solution  of  potassium  sulphate  is  prepared 


MANUFACTURE  OF  SULPHOCYANIDES.          279 

in  the  boilers,  so  that  the  amount  of  this  salt  is  somewhat  greater 
than  that,  which  is  exactly  necessary  for  the  conversion  of  the  am- 
monium  sulphocyanate.  Then  the  calcium  sulphocyanide  is  run  in 
in  small  portions  at  a  time,  the  stirrers  being  set  in  motion  after  each 
addition.  Calcium  sulphate  is  precipitated.  The  resulting  mash 
is  subjected  to  filter-presses  in  order  to  separate  the  calcium  sulphate. 

As  the  filtrate  still  contains  some  calcium  sulphocyanate,  unde- 
composed,  the  latter  is  precipitated  with  potassium  carbonate,  and 
after  filtration  the  filtrate  is  evaporated  at  125°  and  crystallized. 
Besides  sulphocyanide  of  potash,  this  solution  contains  some  sulphate, 
chloride  and  carbonate  of  potash,  which  latter  salts  crystallize  first. 
These  crystals  are  removed  and  the  remaining  solution  is  evaporated 
to  dryness,  this  solution  containing  only  potassium  sulphocyanide. 
The  residue  is  fused  at  300°  in  deep,  wide  pans,  made  of  cast  iron,  and 
thus  yields  a  product  as  pure  as  possible. 

It  now  only  remains  to  convert  the  sulphocyanide  into  potassium 
ferrocyanide.  Although  the  study  of  this  preparation  does  not 
exactly  belong  to  the  scope  of  this  chapter,  and  has  already  been 
discussed  in  a  preceding  chapter,  a  few  words  will  be  said,  because  of 
the  fact  that  Tcherniac  and  de  Giinzburg's  process  has  especially  to 
do  with  the  production  of  potassium  ferrocyanide. 

These  investigators  carry  out  this  conversion  as  follows:  The 
potassium  sulphocyanide,  as  above  obtained,  is  pulverized  and  inti- 
mately mixed  with  powdered  reduced  iron,  or  sifted  cast-iron  powder 
The  mixture  is  quickly  introduced  into  metallic  boxes  with  covers,  A 
(Fig.  25),  which  are  placed  in  a  sulphur  stove  kept  at  a  temperature 
of  about  450°,  the  stove  being  heated  directly  over  the  fire.  When 
the  operation  is  finished  the  boxes  are  removed  and  placed  in  another 
stove  hermetically  sealed  and  surrounded  with  cold  water,  where 
they  are  thus  cooled  out  of  contact  with  air.  The  fused  and  cooled 
mass,  consisting  of  a  mixture  of  iron  sulphide  and  potassium  cyanide, 
according  to  the  reaction 

CNSK+Fe=FeS+CNK, 

is  treated  with  water,  and  yields  a  solution  of  potassium  ferrocyanide 
containing  30-35%  of  this  salt,  which  it  is  only  necessary  to  purify 
by  evaporation  and  crystallization. 


280       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

This  last  part  of  Tcherniac  and  de  Giinzburg's  process  was  for. 
a  long  time  the  cause  of  the  failure  of  the  method.  It  was  not  until 
much  feeling  about  and  numerous  investigations  that  these  inventors 
succeeded  in  evolving  the  following  conditions  which  assure  the 
success  for  the  method: 


FIG.  25. 

(1)  The  sulphocyanate  should  be  perfectly  dry  and  pure. 

(2)  The  iron  should  be  free  from  rust  and  impurities. 

(3)  The  mixture  should  be  as  intimate  as  possible. 

(4)  The  temperature  of  fusion  should  be  450°;   no  higher  than 
500°,  no  lower  than  300°. 

(5)  The  fusion  and  the  cooling  should  take  place  out  of  contact 
with  air. 

If  all  these  conditions  are  not  strictly  followed  the  results  may 
be  defective. 


MANUFACTURE  OF  SULPHOCYANIDES.  281 

Such  is  the  process  of  Tcherniac  and  de  Giinzburg;  it  occupies 
an  important  place  in  the  history  of  the  cyanide  industry,  and  has 
given  results  truly  remarkable;  it  is  one  of  the  few  processes  that 
has  lived.  Other  manufacturers  have  been  animated  by  the  works 
and  the  process  of  Tcherniac  and  de  Giinzburg,  which  they  have  to 
some  extent  improved. 

Deiss  and  Monnier's  Process. — Thus  it  is  that  the  Deiss  and 
Monnier  Company  of  Saint-Denis  (Patent  No.  217,825,  Dec.  3, 
1891;  March  2,  1892)  recommend  preparing  sulphocyanides  by  the 
action  not  of  an  aqueous  solution  of  ammonia,  but  of  gaseous  am- 
monia on  carbon  bisulphide.  According  to  these  inventors,  the 
reaction  is  more  rapid,  and  larger  amounts  of  raw  materials  may 
be  treated  in  small  and  less  complicated  apparatus  than  that  of 
Tcherniac's  process.  Moreover,  the  reaction  takes  place  in  the 
cold  and  at  a  normal  pressure,  which  therefore  requires  less  costty 
apparatus.  The  process  is  otherwise  carried  on  as  follows:  The 
sulphide  is  mixed  with  rich  carbides  (petroleum,  vegetable  or  mineral 
oils,  higher  alcohols,  e.g.,  butyl  or  amyl,  etc.),  to  the  extent  of  30 
to  50%.  By  means  of  a  pump  this  mixture  is  brought  in  contact 
with  ammonium  sulphide,  the  object  of  which  is  to  dissolve  the 
thiosulphocarbonate  as  fast  as  it  is  formed,  the  mixture  being  kept 
cold  by  means  of  running  cold  water.  Ammonium  thiosulpho- 
carbonate is  immediately  formed.  When  the  whole  of  the  carbon 
bisulphide  is  combined,  the  solution  of  thiosulphocarbonate,  sepa- 
rated from  the  carbide  by  decantation,  is  run  into  an  apparatus 
which  is  heated  externally  by  a  coil  of  steam,  where  this  salt  is 
decomposed  into  ammonia  and  hydrogen  sulphide,  which  are  set 
free,  and  into  ammonium  sulphocyanide,  which  remains  in  the  still. 
This  latter  solution  is  concentrated  and  allowed  to  crystallize.  The 
hydrogen  sulphide  set  free  in  this  reaction  is  conducted  into  a  washer 
containing  ,oil,  where  it  leaves  behind  the  carbon  bisulphide,  which 
was  entrained.  Some  ammonium  sulphydrate  is  likewise  formed 
by  the  action  of  the  gaseous  ammonia  on  hydrogen  sulphide,  and 
this  is  collected  in  a  receiver  containing  water. 

The  reaction  pointed  out  by  Millon  and  Gelis  successively, 

CS2 +4NH3 =CNS  -NH4  +  (NH^aS, 
converts  only  half  of  the  ammonia  used  in  the  reaction  into  cyanogen. 


282       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

compounds;  the  other  half,  to  a  large  extent  at  least,  being  converted 
into  ammonium  sulphide  and  ammonium  sulphydrate.  Now,  then,  the 
ammonium  sulphide  causes  an  enormous  pressure  inside  the  apparatus, 
which  necessitates  special  appliances  very  costly  and  complicated. 

Means  of  overcoming  the  serious  objection  of  the  formation  of 
ammonium  sulphide  have  therefore  been  sought.  All  the  improve- 
ments to  Gelis's  reaction  toward  this  end  depend  upon  the  same 
principle:  The  absorption  of  the  hydrogen  sulphide  by  a  non- volatile 
base,  which  diminishes  the  pressure  appreciably;  since,  for  example, 
the  pressure  of  calcium  sulphydrate  at  the  boiling-point  is  not 
greater  than  that  of  water,  whereas  that  of  ammonium  sulphide  is 
about  seven  times  greater  (A.  E.  Wareing).  Moreover,  the  ammonia 
is  thus  rendered  free  for  the  conversion  into  sulphocyanide. 

Hood  and  Salomon's  Process.  —  One  of  the  first  improvements 
along  this  line  is  that  of  Hood  and  Gordon  Salamon.  (English 
patent  No.  5534,  1891,  and  German  patent  No.  12018,  Feb.  27,  1892; 
Aug.  3, 1893).  It  consists  in  treating  while  hot,  a  mixture  of  carbon 
bisulphide  and  ammonia,  in  the  presence  of  a  mixture  of  lime  and 
an  oxidizing  agent,  such  as  manganese  peroxide.  ("For  this  pur- 
pose Wei  don  mud  well  washed  in  order  to  completely  remove  the 
calcium  chloride  may  be  taken"),  or  ferric  oxid,  etc. 

The  operation  is  conducted  in  a  boiler  autoclave,  into  which  the 
mixture  of  lime  and  oxid  of  manganese  is  introduced,  after  which 
the  apparatus  is  heated  to  100°,  when  the  carbon  bisulphide  and 
ammonia,  mixed  in  molecular  proportions,  are  added  a  little  at  a 
time.  When  the  reaction  is  finished  the  product  is  tahen  up  with 
water  which  dissolves  the  calcium  and  manganese  sulphocyanates, 
leaving  an  insoluble  residue  of  manganese  sulphide  and  sulphur. 
These  latter  are  separated  by  filtration;  from  the  residue  the  man- 
ganese dioxide  is  revivified  and  again  used.  The  filtered  solution  is 
treated  with  an  alkali  carbonate  in  order  to  precipitate  the  lime  and 
manganese  and  to  convert  their  sulphocyanates  into  alkali  sulpho- 
cyanate.  This  precipitation  is  fractionated,  the  manganese  having 
a  greater  affinity  for  the  carbonic  acid  than  the  lime  has;  and  so 
manganese  carbonates  separates  out  first. 

Brock's  Process. — Somewhat  similar  is  the  process  of  J.  Brock, 
A.  E.  Hetherington,  P.  Hurter,  J.  Raschen  (English  patent  No.  21451, 
Nov.  1893;  Dec.  1894).  In  the  course  of  their  researches  on  this 


MANUFACTURE  OF  SULPHOCYANIDES.  283 

important  question  these  chemists  noticed  that  the  presence  of 
manganese  and  iron  oxides  was  superfluous,  and  that  the  lime  alone 
sufficed.  Their  process  consists,  therefore,  in  heating  in  a  cylin- 
drical apparatus,  made  of  cast  iron  or  steel  and  placed  horizontally, 
a  mixture  of  carbon  bisulphide,  ammonia,  and  lime  in  the  following 
proportions : 

Carbon  bisulphide 100  parts 

Slaked  lime 200    ". 

Ammoniacal  solution  containing. 45    "! 

dry  .ammonia-gas,  together  with  a  sufficient  amount  of  water  to 
make  the  mass  fluid. 

The  amount  of  ammonia  used  is  twice  that  required  by  the 
equation 

2CS2 + 2NH3  +  2Ca(OH)  a = Ca(CNS)  2 + CaS2H2 + 4H20. 

The  cylinder  has  double  walls,  steam  circulating  between  the 
walls,  bringing  the  temperature  of  the  interior  and  its  contents  to 
100°  C.  The  cylinder  is  provided  with  a  mechanical  stirrer,  which 
allows  the  mass  to  be  continually  stirred  during  the  reaction,  lasting 
from  2  to  6  hours.  The  same  bottom  through  which  the  stirrer 
passes  is  provided  also  with  a  safety-valve,  an  outlet  tube  for  draw- 
ing off,  and  a  lid  for  the  charging.  A  thermometer  and  a  manom- 
eter allow  the  temperature  and  pressure  to  be  watched. 

After  driving  off  the  excess  of  ammonia  by  distillation  the  whole 
is  filtered  in  order  to  remove  the  lime,  and  carbonic  acid  is  passed 
through  the  product.  Under  these  conditions  the  calcium  sul- 
phide and  the  calcium  sulphydrate  are  decomposed,  hydrogen  sul- 
phide is  set  free  and  driven  off,  and  carbonate  of  lime  is  precipi- 
tated. After  filtering  there  remains  a  solution  of  calcium  sulpho- 
cyanide  which  may  be  treated  by  any  of  the  appropriate  methods 
for  ts  conversion  into  alkali  sulphocyanide. 

Process  of  the  British  Cyanide  Company. — This  process  (German 
patent  No.  14611,  April  16,  1894;  Jan.  10,  1895)  consists,  likewise,  in 
causing  ammonia  to  act  on  carbon  bisulphide  in  the  presence  of  a 
base,  such  as  lime,  without  the  use  of  any  oxidizing  agent.  The 
apparatus  used,  a  double-walled  autoclave  cylinder  provided  with 
a  stirrer,  differs  but  little  from  that  of  the  preceding  process.  It 


284   METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

is  first  charged  with  17-18.5  parts  of  an  ammoniacal  solution  con- 
taining 7.15%  dry  gas,  101-102  parts  hydrated  lime,  finely  powdered, 
containing  72-75%  CaO. 

These  two  substances  are  intimately  mixed  and  then  are  added 
76  parts  carbon  bisulphide;  the  autoclave  is  closed  and  heated 
gently,  the  stirrer  being  kept  in  motion,  when  the  manometer  indi- 
cates 2  atmospheres  pressure  the  heating  is  discontinued;  the  pres- 
sure continues  to  rise  up  to  6  atmospheres,  when  it  falls. 

At  this  point  the  heat  is  again  applied  till  the  temperature  of 
115-120°  is  reached,  andvthis  is  maintained  for  several  hours. 

As  in  the  preceding  process,  the  product  of  the  reaction  is  treated 
with  carbonic  acid  which  displaced  hydrogen  sulphide  from  the 
calcium  sulphide  and  the  calcium  sulphydrate.  The  carbonate  of  lime 
is  separated  by  filtration,  the  filtrate  which  contains  only  sulphocyan- 
ide  being  treated  with  an  alkali  salt  which  thus  yields  alkali  sulpho- 
cyanide  on  evaporation  and  crystallization.  The  first  part  of  the 
evaporation  takes  place  in  a  distilling  apparatus  in  the  presence  of 
caustic  soda,  and  at  boiling  temperature  in  order  to  recover  the  small 
amount  of  ammonia  remaining  in  solution  (about  5%).  The  hydro- 
gen sulphide  set  free  may  either  be  burned  in  order  to  yield  sul- 
phurous acid  to  be  used  in  feeding  the  lead  chambers,  or  else  treated 
in  the  ordinary  way  for  the  extraction  of  sulphur  from  it.  Conroy, 
who  has  made  a  whole  series  of  investigations  on  these  processes, 
clears  up  this  subject  considerably  in  an  interesting  paper  in  The 
Journal  of  the  Society  of  Chemical  Industry  (1896).  From  the  in- 
vestigations conducted  by  this  English  savant,  in  collaboration 
with  Zahortki,  it  follows  that: 

(1)  An  excess  of  ammonia  is  absolutely  indispensable  to  carry 
on  the  reaction  properly,  as  it  is  well  known  that  in  this  reaction 
thiocarbonate  of  lime  is  also  formed, 

3CS3 + 2Ca(OH)  2  =  2CaS3C + 2H20 + C02, 
which  in  contact  with  water  gives 

CaCS3+3H20=  3H2S+CaC03, 

unless  there  is  an  excess  of  ammonia,  and  in  this  case  the  reaction 
becomes 

2CaCS3 + 2NH3  =  (CNS)  2Ca  +  3H2S + CaS. 


MANUFACTURE  OF  SULPHOCYANIDES.  285 

(2)  The  addition  of  lime  does  not  exert  any  influence  on  the 
yield  of  sulphocyanate;  it  serves  only  to  diminish  the  pressure. 

(3)  Carbon  bisulphide  and  calcium  sulphide  unites  in  order  to 
form  soluble  calcium  sulphocarbonate,  and  this  union  is  best  made 
at  the  temperature  of  50-60°. 

(4)  The  solution  of   calcium  thiocarbonate  may    be    converted 
quantitatively  into  sulphocyanate;   but  in  order  to  obtain  a  favor- 
able yield  it  is  necessary  to  work  under  pressure  and  in  the  presence 
of  a  large  excess  of  ammonia. 

Albright's  Process.  —  A  later  improvement  along  this  line,  is  that 
brought  about  by  G.  S.  T.  Albright,  at  Birmingham  (German  patent 
No.  4324,  May  4,  1895;  October  21,  1895).  It  consists  practically  in 
making  use  of  magnesia  instead  of  lime.  Under  pressure,  magne- 
sium hydrate  fixes  hydrogen  sulphide,  which  is  set  free  by  the  action 
of  carbon  bisulphide  on  ammonia  in  order  to  form  magnesium 
sulphydrate;  and  this  salt  again  liberates  hydrogen  sulphide  on 
boiling,  while  at  the  same  time  magnesium  hydrate  is  reproduced 
and  may  be  used  for  the  next  operation: 


+  2H2S=MgH2S2+2H20; 
MgH2S2+2H20  =  Mg(OH)2+2H2S. 

The  operation  is  carried  on  in  a  boiler  provided  with  a  stirrer 
where  magnesium  sulphocyanide  is  at  the  same  time  produced.  It 
is  well  to  add  to  the  magnesia  a  sufficient  quantity  of  lime  to  fix 
completely  the  sulphocyanic  acid  formed.  The  insoluble  magne- 
sium hydrate  is  separated  by  filtration  from  the  calcium  sulpho- 
cyanide, which  latter  is  then  converted  into  alkali  sulphocyanide 
by  double  decomposition  with  an  alkali  sulphate  or  carbonate. 

Tcherniac's  Process.  —  Another  class  of  methods  for  the  pro- 
duction of  sulphocyanides  makes  use  of  nitrites,  carbon  bisulphide, 
and  hydrogen  sulphide.  Such  are  the  processes  of  Tcherniac, 
Goerlich  and  Wichmann.  This  process  had  already  in  1856  been 
pointed  out  by  Schlagdenhaufen,  who  had  observed  that  by  heating 
carbon  bisulphide  and  a  nitrite  in  a  closed  tube  there  were  formed 
sulphocyanate,  carbonic  acid,  and  hydrogen  sulphide,  but  that 
under  these  conditions  a  large  portion  of  the  carbon  bisulphide 
burns  with  the  formation  of  sulphuric  and  carbonic  acids,  and  at  the- 


'286       METHODS   OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

same  time  a  large  part  of  the  nitrogen  was  lost  as  free  nitrogen  or  in 
the  form  of  nitrogen  protoxide.  If,  on  the  contrary,  as  is  done  in 
Tcherniac's  process,  a  mixture  of  carbon  bisulphide,  nitrite,  and 
hydrogen  sulphide  be  heated  in  an  autoclave  an  almost  quantitative 
yield  of  sulphocyanide  is  obtained. 

Tcherniac's  process  consists  (French  patent  No.  248163,  June  14, 
1895;  Oct.  16,  1895)  in  heating  the  following  mixture  in  an  auto- 
cla,ve  provided  with  a  mechanical  stirrer: 

Nitrate  of  the  base  usea 1  molecule 

Carbon  bisulphide 1 

Hydrogen  sulphide 2  molecules 

The  hydrogen  sulphide  may  first  be  made  to  act  on  the  nitrite,  or 
<else  be  compressed  into  the  autoclave,  which  is  heated  to  150°  C. 
until  the  manometer  indicates  a  depression,  which  shows  the  end  of 
the  reaction.  This  may  be  expressed  thus: 

RN02 +CS2  +2H2S =CNRS +S3  +2H20. 

In  order  to  make  use  of  the  whole  of  the  nitrite  the  hydrogen 
sulphide  should  be  in  slight  excess.  The  sulphur  separates  from  the 
aqueous  solution  of  the  sulphocyanide,  in  the  form  of  a  crystalline 
crust,  very  easy  to  remove,  and  the  sulphocyanide  obtained  is  almost 
pure,  and  may  be  used  for  any  purpose  in  the  arts. 

Goerlich  and  Wichmann's  Process. — This  process  (German  patent 
No.  9831,  June  7,  1895;  July  30,  1896)  is  identical  in  every  respect 
with  that  of  Tcherniac's. 

Finally,  it  only  remains  to  mention  Goldberg  and  Siepermann's 
process  (German  patent  No.  9494,  Jan.  14,  1895;  June  13,  1895).  It 
consists  in  heating  under  pressure  a  mixture  of  carbon  bisulphide, 
ammonia,  and  alkali-  or  alkaline-earth  sulphite  or  bisulphite.  The 
reaction  which  already  begins  at  100°,  goes  on  actively  at  120 
to  130°  by  stirring  constantly,  and  especially  if  the  operation  is 
carried  on  in  the  presence  of  an  alkaline-earth  sulphite. 

In  a  general  way  the  reactions  may  be  expressed  by  the  following 
equations  in  the  case  of  an  alkaline  base : 


MANUFACTURE   OF  SULPHOCYANIDES.  287 

2CS2 + 2NH3  +  R2S03  =2CNRS  +  3S  +  3H20, 
2CS2 + 2NH3  +  R2S203  =2CNRS + 4S  +  3H20, 

or  in  the  case  of  an  alkaline-earth  base  (lime,  magnesia), 

2CS2+2NH3+RS03  =  (CNS)2R+3S+3H20, 
2CS2 + 2NH3 + RS203  =  (CNS)  2R + 4S + 3H20. 

The  sulphur  thus  formed  is  collected  as  fast  as  it  is  formed  under 
the  solution  of  sulphocyanide  in  the  form  of  a  fused  mass. 


CHAPTER  X. 

MANUFACTURE    OF    PRUSSIAN    BLUE    AND   VARIOUS    OTHER 

COMPOUNDS. 

PRUSSIAN  blue,  or  ferric  ferrocyanide,  was,  as  we  have  already 
mentioned,  the  first  cyanogen  compound  known.  Its  discovery 
occupies  a  very  important  place  in  the  history  of  chemical  industry, 
for  it  is  in  consequence  of  this  happy  finding  that  all  the  cyanogen 
compounds  were  produced. 

The  discovery  of  Prussian  blue  dates  back  to  the  year  1710,  and 
like  that  of  many  chemical  products  it  was  due  purely  to  chance. 
A  Berlin  manufacturer  of  colors,  named  Diesbach,  wishing  to  precipi- 
tate cochineal  lake  by  means  of  potash,  and  not  having  any  of  this 
substance  on  hand  borrowed  some  of  a  pharmacist  of  that  city, 
Dippel  by  name.  This  pharmacist  gave  him  some  potassium  car- 
bonate which  he  had  used  in  rectifying  an  empyreumatical  oil,  of 
animal  origin,  of  the  same  name.  When  Diesbach  made  use  of  this 
product,  instead  of  the  red  lake  which  he  wished  to  prepare,  he 
obtained  a  magnificent  blue  precipitate.  Surprised  at  this  extraor- 
dinary phenomenon  he  took  Dippel  into  his  confidence,  who  was 
not  slow  in  suspecting  that  this  precipitate  was  due  to  the  action 
of  potash  on  iron  alum,  which  Diesbach  had  used.  In  fact,  on 
repeating  the  experiment  Dippel  obtained  an  absolutely  similar 
result.  From  that  time  he  resolved  to  make  something  out  of  this 
remarkable  discovery.  In  a  paper  which  he  presented  to  the  Acad- 
emy of  Berlin  in  1710  he  calls  attention  to  this  body,  without 
however  disclosing  the  mode  of  preparation,  and  he  joined  with 
Diesbach  in  the  manufacture  of  this  new  product.  The  method 
of  manufacture  was  kept  secret  till  1724,  at  which  time  an  English 
chemist,  Woodward,  member  of  the  Royal  Society  of  London,  suc- 
ceeded in  reproducing  Prussian  blue,  and  made  public  the  method 

288 


MANUFACTURE  OF  PRUSSIAN  BLUE.  289 

of  preparation.  This  publication  created  a  great  sensation  at  the 
time,  for  with  the  exception  of  indigo  no  other  blue  coloring-matter 
was  known.  Woodward's  method,  practically  unchanged,  is  the  one 
carried  on  to-day  in  the  works  where  Prussian  blue  is  prepared. 

It  was  begun  by  preparing  a  " blood-lye"  obtained  by  treating 
with  hot  water  the  product  of  ignition  of  dried  blood  or  other  organic 
materials  in  the  presence  of  potassium  carbonate.  This  lye  was 
then  exposed  to  air  in  shallow  pans  until  a  lead  salt  gave  no  longer 
a  precipitate,  and  then  treated  with  a  mixed  solution  of  alum  and  « 
copperas.  The  whole  was  constantly  stirred  with  a  stick,  a  bri^/ 
effervescence  taking  place,  while  at  the  same  time  a  greenish  precipi- 
tate was  formed.  It  was  allowed  to  stand  for  some  time,  and  then  de- 
canted, the  precipitate  being  washed  with  water  until  it  had  acquired 
a  blue  color.  It  was  then  drained,  compressed  in  the  form  of  cubes 
which  were  allowed  to  dry  in  the  open  air  by  means  of  gentle  heat. 

Prussian  blue  is  also  formed  when  ferrocyanide  of  potassium  or 
barium  or  ferrohydrocyanic  acid  is  precipitated  by  means  of  a  salt 
of  iron  peroxide,  or  when  potassium  cyanide  is  precipitated  by  a 
ferro-ferric  salt: 

18KCN + 3FeCl2 + 2Fe2Cl6  =  18KC1 + Fe7(CN)  18. 

It  is  formed  by  the  action  of  hydrocyanic  acid  on  ferro-f erric- 
hydrate,  or  of  a  ferric  salt  on  ferrous  cyanide, 

9Fe  (CN)  2 + 2Fe2Cl6 = Fe7(CN)  18 + 6FeCl2, 

or  by  the  action  of  an  oxidizing  agent,  such  as  chlorine- water  on 
ferrous  cyanide,  hydroferrocyanic  acid,  ferro-potassic-cyanide. 

The  best  method  of  obtaining  a  splendid  quality  of  Prussian  blue 
is  to  precipitate  potassium  ferrocyanide  with  an  acid  solution  of 
sulphate  of  iron  protoxide  (ferrous  sulphate,  green  vitriol,  copperas). 
This  is  done  in  the  following  manner : 

Potassium  ferrocyanide  and  ferrous  sulphate  are  separately 
dissolved  in  15  times  heir  weight  of  water,  or  else  a  solution  of 
each  is  prepared  by  dissolving  6  parts  of  the  salt  in  15  parts  water. 
The  solutions  are  then  mixed,  and  while  constantly  stirring,  a 
mixture  of  1  part  concentrated  sulphuric  acid  and  24  parts  fum- 
ing hydrochloric  acid  is  added. 


290       METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

A  grayish-white  precipitate  of  ferro-potassic-ferrocyanide  is 
formed,  the  mother-liquors  containing  potassium  sulphate  which 
may  be  removed  by  evaporation.  The  precipitate  is  allowed  to 
stand  several  hours,  and  then  it  is  washed  with  a  large  amount  of 
water.  It  remains  only  to  make  it  blue,  i.e.,  to  oxidize  it.  Under 
the  influence  of  atmospheric  oxygen  or  of  any  oxidizing  agent,  the 
ferro-potassic-ferrocyanide  is,  in  fact,  converted  into  Prussian  blue: 


+  03=Fe7(CN)i8+3FeK4(CN)6+re203. 

As  may  be  supposed,  many  methods  have  been  used  in  the  oxida- 
tion of  ferro-potassic-ferrocyanide. 

First,  air  was  used.  This  is  the  oldest  method,  and  the  one 
which  gives  the  poorest  results. 

Solutions  of  clarified  hypochlorite  of  lime  have  likewise  been 
much  used,  this  solution  being  added  in  small  quantities  at  a  time. 
But  although  this  process  has  been  used  a  long  time  it  has  the 
objection  of  forming  calcium  sulphate,  which  is  only  slightly  soluble 
together  with  the  Prussian  blue,  which  former,  in  mixing  with  the 
Prussian  blue,  weakens  the  color  just  so  much,  or  at  least  forms 
white  spots  in  the  blue  which  depreciates  the  value. 

In  his  "  Traite  de  Chimie  appliquee  aux  Arts  industriels  "  Girardin 
gives  a  formula  for  making  Prussian  blue  by  means  of  hypochlorite 
of  lime.  The  work  is  carried  on  as  in  the  preceding,  by  precipi- 
tating copperas  with  prussiate  in  the  following  proportions: 

Crystallized  ferrocyanide  ...................  10  parts 

Copperas  .................................  11 

The  precipitate  formed  is  treated  with  hypochlorite  of  lime: 
Chloride  of  lime  dissolved  in  100  parts  of  water  .........  1.5  parts 

and  then  with  weak  hydrochloric  acid: 

Hydrochloric  acid  diluted  with  100  parts  of  water  .........  5.0  parts 

Aqua  regia  at  ordinary  temperature  and  chromic  acid  have 
also  been  used,  both  of  which  methods  have  been  abandoned,  the 
first  being  too  costly  and  the  latter  being  objectionable  on  account 
of  its  leaving  chrome  alum,  which  is  of  little  use,  in  the  mother- 
liquors.  In  the  latter  case,  the  treatment  was  carried  on  as  fol- 


MANUFACTURE  OF  PRUSSIAN  BLUE.  291 

lows :  A  solution  of  10  kg.  of  bichromate  of  potash  in  100  liters  of 
hot  water  was  made;  after  cooling,  135  kg.  of  sulphuric  acid  (com.) 
was  added,  and  this  mixture  was  gradually  poured  on  the  white 
precipitate  potassic  ferro-ferrocyanide,  which  was  diluted  with  boil- 
ing water  until  the  precipitate  had  acquired  a  beautiful  intense- 
blue  color. 

A  boiling  solution  of  potassium  chlorate  may  profitably  be  used, 
but  the  best  procedure  is  that  which  consists  in  using  a  warm  solu- 
tion of  iron  perchloride  or  of  ferric  sulphate.  When  this  solution 
acts  on  the  white  precipitate,  it  is  brought  back  to  the  state  of  proto- 
salt,  which  may  then  be  treated  with  ferrocyanide  and  be  used 
anew. 

Whether  the  oxidation  of  ferro-potassic-ferrocyanide  be  carried 
on  by  one  or  other  of  the  above  methods,  the  conversion  into  Prus- 
sian blue  is  never  complete,  for  another  part  of  the  white  precipi- 
tate produces  a  compound  which  is  also  blue,  and  which  seems 
to  be  a  ferri-potassic-ferricyanide. 

Although  the  preparation  of  Prussian  blue  seems  at  first  sight 
very  simple,  it  nevertheless  requires  care  if  a  pure  product  of  beau- 
tiful shade  is  to  be  obtained.  The  essential  conditions  which  apply 
to  all  the  methods  just  described  are  the  following: 

(1)  The  iron  solution  should  always  be  poured  into  the  potas- 
sium ferrocyanide  and  never  the  reverse,  if  it  be  not  desired  that 
the  precipitate  formed  should  enclose  a  large  quantity  of  potas- 
sium ferrocyanide.  (2)  It  is  well  to  digest  the  Prussian  blue  with 
hydrochloric  or  nitric  acid  in  order  to  remove  the  iron  oxid  com- 
pletely, which  always  reduces  more  or  less  the  intensity  of  the  color. 

The  iron  salt  used  should  be  as  pure  as  possible,  and  especially 
should  not  contain  copper,  since  the  salts  of  this  metal  with  ferro- 
cyanide give  a  reddish  precipitate  which  injures  the  brilliancy  of  the 
tint. 

In  the  preparation  of  ordinary  commercial  Prussian  blues,  alum 
in  various  amounts  is  very  often  added  at  the  moment  of  the  pre- 
cipitation. The  alum  salt  forms  aluminum  ferrocyanide,  which  has 
the  gelatinous  appearance  of  aluminium,  it  being  intimately  mixed 
and  held  in  the  Prussian-blue  precipitate,  increasing  the  weight 
without  appreciably  injuring  the  tint,  unless  too  great  amounts 
are  used. 


'292      METHODS  OF  MANUFACTURING  CYANIDE  COMPOUNDS. 

The  alum  is  added  in  various  amounts  according  to  the  quality 
of  Prussian  blue  desired.  For  pure  blues,  not  any  is  added. 

For  a  fine  quantity  of  blue,  one  part  of  alum  is  used  for  three  or 
four  parts  of  ferrous  sulphate;  for  an  ordinary  blue,  one  part  to  two 
or  three  of  iron  sulphate;  and  for  blues  of  inferior  quality,  equal 
parts  of  the  two  salts.  In  certain  blues  of  very  low  quality,  as  much 
as  three  parts  of  alum  are  used  for  one  of  ferrous  sulphate. 

Moreover,  the  varieties  of  Prussian  blue  are  very  numerous,  and 
the  quality  of  this  product  depends  altogether  on  its  mode  of  prepara- 
tion. There  are  fifteen  or  twenty  classes  of  Prussian  blue,  all  differ- 
ing from  one  another  in  their  composition  and  color.  The  principal 
ones  are:  Berlin  blue,  Prussian  blue  of  Paris  or  Milori  blue,  Paris 
blue,  fine  and  dark,  ordinary  deep  blue,  and  mineral  or  Antwerp 
blue,  to  which  oxid  of  zinc  or  magnesium  carbonate  is  often 
added. 

Soluble  Prussian  blue. — This  compound,  whose  exact  composition 
is  not  yet  known,  and  which  according  to  some  is  a  union  of  or- 
dinary Prussian  blue  and  potassium  ferrocyanide,  and  according  to 
others  a  ferricyanide  of  iron  and  of  potassium,  is  formed  when  a 
salt  of  iron  peroxid  (iron  perchloride)  is  precipitated  by  potassium 
ferrocyanide  in  excess.  The  precipitate  thus  formed  is  a  very 
beautiful  blue  insoluble  in  the  solution  containing  potassium  ferro- 
cyanide, but  soluble  in  pure  water. 

It  is  likewise  obtained  when  a  solution  of  iron  iodide  containing 
an  excess  of  iodine  is  poured  into  a  concentrated  solution  of  potas- 
sium ferrocyanide  (Reade).  The  blue  precipitate  thus  formed  is 
entirely  soluble  in  water,  even  after  drying. 

Turnbull's  blue. — TurnbulPs  blue  is  really  a  ferrous  ferricyanide, 
Fe5(CN)i2.  Its  tint  is  still  a  more  beautiful  blue  than  that  of 
Prussian  blue.  It  is  obtained  by  gradually  pouring  a  hot  solution 
•of  potassium  ferricyanide,  free  from  ferrocyanide,  into  a  solution 
of  a  ferrous  salt.  This  should  be  allowed  to  stand  some  time  in 
the  presence  of  an  iron  salt,  if  it  be  desired  to  obtain  a  product 
free  from  potash.  It  may  be  distinguished  from  ordinary  Prussian 
blue  by  treating  it  with  a  hot  potash  solution,  when  it  yields  a 
precipitate  of  ferro-ferric  hydrate  and  yellow  prussiate,  whereas 
Prussian  blue  gives  ferric  hydrate. 

Monthiers'  blue,  or  ammoniacal  Prussian  blue. — This  compound, 


MANUFACTURE  OF  PRUSSIAN  BLUE.  293 

which  is  more  stable  than  ordinary  Prussian  blue,  is  a  ferric  iron  and 
ferric  ammonium  ferrocyanide,  its  formula  being 


Monthiers  obtained  it  as  follows:  An  ammonia  solution  is  poured 
into  a  pure  solution  of  iron  protochloride,  the  precipitate  is  rapidly 
filtered,  taking  all  precautions  to  avoid  contact  with  air,  and  the 
filtrate  is  gradually  poured  into  a  solution  of  potassium  ferrocyanide. 
A  white  precipitate  which  becomes  blue  on  contact  with  air  and  also 
a  precipitate  of  ferric  hydrate  are  formed.  By  treating  with  ammo- 
nium tartrate  for  several  hours  at  60-80°,  the  ferric  hydrate  may 
be  removed,  the  ammoniacal  Prussian  blue  being  insoluble.  This 
is  washed  with  water. 

Antimony  blue.  —  This  is  nothing  more  than  a  Prussian  blue  of  a 
beautiful  shade,  obtained  in  a  special  way,  and  falsely  called  anti- 
mony blue,  as  it  contains  no  trace  of  this  metal.  It  is  obtained 
by  boiling  with  potassium  ferrocyanide  the  white  precipitate  formed 
when  a  tartar  emetic  solution  is  treated  with  concentrated  hydro- 
chloric acid;  the  blue  precipitate  formed  is  repeatedly  treated  with 
hydrochloric  acid  in  order  to  remove  the  antimony  completely. 
The  antimony  salt  seems,  therefore,  to  play  no  part  except  to  facili- 
tate the  formation  of  this  compound. 


PART  FOUR. 
THE  USE  OF  CYANOGEN  COMPOUNDS. 


FORMERLY  the  cyanide  industry  owed  its  importance  to  the  use 
of  Prussian  blue  and  of  potassium  ferrocyanide.  Potassium  cyanide 
had  but  limited  application  in  medicine,  in  photography,  in  labora- 
tories (as  a  reagent),  and  in  the  art  of  gilding  and  electrotyping.  The 
chemical  industry  was  therefore  interested  in  the  production  of  the 
first  two  compounds.  To-day  the  reverse  is  true,  Prussian  blue 
finds  but  limited  uses,  50%  of  the  potassium  ferrocyanide  products 
being  converted  into  potassium  cyanide,  and  of  all  the  cyanogen 
compounds  the  latter  is  the  one  most  in  use. 

It  has  already  been  mentioned  that  the  chief  application  of  this 
salt  is  in  the  extraction  of  gold  from  its  minerals,  and  it  is  due  to 
this  one  use,  which  has  become  of  considerable  importance,  that  the 
industry  of  cyanogen  and  its  compounds  owes  its  present  develop- 
ment. 

Although  the  question  of  the  treatment  of  gold  minerals  belongs 
rather  to  a  metallurgical  treatise,  we  must,  however,  mention  the 
subject  on  account  of  its  importance  and  the  close  bonds  which  unite 
it  with  the  cyanide  industry. 

In  fact,  the  methods  for  the  extraction  of  gold  by  means  of  potas- 
sium cyanide  have  been  considerably  extended,  and  are  destined 
still  to  increase  and  to  become  universal.  The  results  thus  far  obtained 
are  most  satisfactory  as  well  from  an  economical  standpoint  as  from 
the  standpoint  of  the  yield,  and  there  is  no  doubt  as  to  the  future. 

The  idea,  which  is  the  basis  of  these  processes,  is  old.  The  solu- 
bility of  gold  in  potassium  cyanide  has  long  been  known.  Faraday 

294 


THE  USE  OF  CYANOGEN  COMPOUNDS.  295 

observed  this  fact,  later  Prince  Bagration  did  the  same.  But  to 
Eisner  belongs  the  honor  of  being  the  first  to  study  the  conditions 
under  which  the  solution  takes  place.  This  investigation  showed 
that  oxygen  was  essential : 

2Au  +  4KCN  +  0  +  H20  =  2K  Au(CN)  2 + 2KOH. 

This  theory  was  vigorously  combatted  by  MacArthur  and  Forest^ 
who  were  the  first  to  think  of  applying  this  reaction  to  the  extraction 
of  gold  on  an  industrial  scale ;  but  to-day  it  is  an  accepted  fact  that 
the  solution  of  gold  in  potassium  cyanide  cannot  take  place  without 
the  help  of  oxygen,  and  is  facilitated  by  the  presence  of  any  oxidiz- 
ing agent  (peroxides  of  sodium,  barium,  lead,  manganese,  perman- 
ganate, bichromate,  nitrates,  chlorate,  potassium  ferricyanide). 

Furthermore,  Christy  (Jr.  Soc.  Chem.  Ind.,  1898,  p.  332)  has 
shown  that  the  presence  of  free  cyanogen  and  potassium  cyanide  is 
absolutely  indispensable,  the  former  being  used  in  the  formation  of 
gold  cyanide,  which  with  the  latter  forms  a  soluble  double  cyanide. 

As  may  be  seen,  the  amounts  of  oxygen  and  of  cyanide  of  potas- 
sium essential  to  the  solubility  of  gold  are  very  small.  If  the  above 
equation  be  considered 

(2  Au  +  4KCY  +  0  +  H20  =  2KAuCy  2 + 2KOH) 

it  will  be  noticed  that  130.4  parts  of  potassium  cyanide  by  weight 
dissolve  196.8  parts  of  gold,  i.e.,  approximately  2  parts  of  cyanide 
to  3  parts  of  gold.  As  to  the  oxygen,  only  15.96  parts  are  required 
to  dissolve  396.6  parts  of  gold,  i.e.,  1  part  oxygen  to  25  parts  precious 
metal.  This  oxygen  is  furnished  in  more  than  sufficient  quantity 
by  the  amount  of  air  occluded  in  the  minerals  and  by  the  oxygen 
dissolved  in  the  water  used  in  the  preparation  of  cyanide  solutions. 

In  practice,  the  amount  of  cyanide  used  is  always  somewhat 
larger  than  that  required  theoretically,  because  the  losses  which  occur 
during  the  "cyaniding"  must  be  taken  into  account.  The  causes 
of  these  losses  have  been  carefully  studied  by  Ch.  Butters,  Clennell, 
and  Mosenthal  (Engineering  and  Mining  Journal,  Oct.  1892),  and 
may  be  thus  set  forth : 

(1)  The  oxidation  of  the  auriferous  minerals,  the  result  of  which 
is  the  precipitation  of  a  part  of  the  potassium  cyanide  in  the 


296  THE  USE  OF  CYANOGEN  COMPOUNDS. 

form  of  Prussian  blue.  The  auriferous  minerals  now  being  worked 
in  South  Africa  almost  always  contain  iron  pyrites,  which  lat- 
ter, under  the  double  action  of  air  and  of  atmospheric  moisture 
become  oxidized,  thus  converting  the  mineral  into  the  form  of  "  free 
milling/'  as  it  is  called  in  the  'Rand,  with  formation  of  iron  sulphate 
and  free  sulphuric  acid: 

FeS2  +  H20  +  70  =  S04Fe  +  S04H2. 

As  the  oxidation  continues  there  are  formed    insoluble  basic 
sulphate  and  insoluble  ferric  sulphate: 


10S04Fe  +50  =2(Fe203)2S03  +3[Fe2(S04)3]. 

Wilstein  Berzelius 

If,  therefore,  a  mineral  of  this  kind  partially  oxidized  be  placed 
in  the  presence  of  a  cyanide  solution  the  ferrous  sulphate  slowly 
acts  on  the  potassium  cyanide,  forming  cyanide  of  iron  and  potas- 
sium sulphate: 

S04Fe  +2CKN  =Fe(CN)2  +S04K2. 

But  in  the  presence  of  a  large  excess  of  potassium  cyanide,  the 
iron  cyanide  becomes  in  its  turn  converted  into  potassium  ferro- 
cyanide,  which,  in  contact  with  ferric  salts,  yields  Prussian  blue: 

Fe(CN)2  +  4KCN=FeK4(CN)6, 
3FeK4(CN)6  +6S04Fe  +30  =Fe203  +  6S04K2  +Fe7(CN)i8. 

This  conversion  may  be  appreciably  avoided  by  adding  caustic  soda 
or  lime  in  order  to  saturate  the  free  acid,  but  nevertheless  there  is 
always  a  partial  conversion  of  cyanide  into  ferrocyanide. 

(2)  The  action  of  the  oxygen  of  the  air  on  cyanide  solutions. 
As  is  well  known,  the  cyanides  are  very  oxidizabie  salts,  the  action 
of  air  converting  them,  first  into  cyanate  and  then  into  carbonate: 


+  0=KCNO, 
2KCNO  +  03  =  C03K2  +  C02  +  N2. 


THE  USE  OF  CYANOGEN  COMPOUNDS.          297 

(3)  The  action  of  carbonic  acid  of  the  air  on  the  cyanide  solu- 
tions : 

2KCN+C02  +  H20=C03K2+2CNH. 

(4)  The  action  of  metals  other  than  gold  existing  in  the  min- 
erals.    The  cyanide  exerts  its  action  on  these  metals,  among  which 
are  most  frequently  met:    copper,  arsenic,  zinc,  nickel,  cobalt. 

A.  W.  Warwick  has  studied  the  solubility  of  gold  in  potassium 
cyanide,  and  from  an  article  published  in  the  Engineering  and 
Mining  Journal,  June  29,  1895,  the  following  conclusions  are  drawn. 

(1)  The  presence  of  oxygen  is  an  important  factor  for  the  solu- 
bility of  gold  in  potassium  cyanide. 

(2)  The  solubility   increases   with  the  temperature.     This  fact 
explains  why  better  results  are  obtained  in  warm  countries  than 
in  those  where  the  climate  is  subject  to  temperature  variations. 

(3)  For  a  given   time    strong  solutions  are  more  active  thart 
dilute  ones. 

(4)  Zinc   exerts  a  prejudicial  action.     It  becomes  precipitated 
on  the  gold  and  causes  the  action  of  the  cyanide  gradually  to  cease. 

(5)  Copper  likewise    exerts  a  decomposing   action,   but  much 
slower. 

(6)  The  presence  of  gold  chloride  much  increases  the  solubility, 
whereas  potassium  chloride  exerts  no  action, 

2AuCl2  +  6KCN  =  2K  Au(CN)  2  +  4KC1 + 2CNC1, 

which  means  that  the  chloride,  bromide,  and  iodide  of  cyanogen 
exert  a  favorable  action  on  the  dissolving  power  of  potassium 
cyanide.  But,  according  to  the  author,  this  action  is  only  indirect, 
and  the  role  of  the  halogen  elements  consists  only  in  setting  free 
the  oxygen  necessary  for  the  solution  of  gold  in  the  cyanide: 

8KCN+Au4+2H20+02=4KCN-AuCN+4KOH, 
4KCN  •  AuCN  +  2CNBr +4KOH=2KCN  •  AuBr +4KCN  +2H20 +02. 

This  formation  of  gold-bromine-cyanide  of  potassium  is  quite, 
probable.  (Lindbom  has,  in  fact,  obtained  this  compound.) 


298          THE  USE  OF  CYANOGEN  COMPOUNDS. 

(7)  The  gold-silver  alloys  dissolve  less  easily  in  potassium  cyanide, 
than  does  pure  gold. 

(8)  Gold  dissolves  less  easily  in  ferrocyanide  and  sulphocyanide 
of  potassium  than  in  the  cyanide. 

Having  given  these  preliminary  principles  let  us  pass  to  the 
work  of  the  extraction  of  gold  by  the  said  cyanide  processes.  To 
McArthur  and  Forest  belongs  the  honor  of  having  had  the  idea 
of  utilizing  the  dissolving  power  of  cyanide  of  potassium.  Their 
process  consisted  in  treating  a  mineral  with  a  dilute  solution  of 
cyanide,  then  to  precipitate  the  gold  out  of  this  solution  by  means 
of  strips  of  zinc.  As  will  be  seen  this  process  has  been  much  improved, 
either  by  its  authors  or  by  other  investigators.  The  treatment 
of  gold  minerals  comprises  two  essential  parts : 

(1)  Solution  of  the  gold  in  the  cyanide. 

(2)  Precipitation  of  the  gold  from  these  solutions. 

Solution. — The  cyaniding  processes  are  especially  used  in  the 
Transvaal  in  the  Wittwatersrand,  or  Rand  district  as  it  -is  most 
generally  called.  It  is  known  that  the  gold  in  the  Transvaal  min- 
erals occurs  in  a  very  finely  divided  condition,  which  makes  amalga- 
mation very  difficult;  it  is  quite  different,  however,  with  the  process 
of  cyaniding,  which  may  be  carried  on  all  the  more  easily  the  more 
finely  divided  the  gold  occurs. 

As  the  mineral  is  brought  out  of  the  mines  it  is  subjected  to  the 
first  sorting,  this  being  done  on  an  inclined  plane,  the  object  being 
to  remove  most  of  the  quartz  and  foreign  matters.  A  second  picking, 
by  hand,  by  means  of  a  current  of  water  removes  the  gangue.  It  is 
then  crushed,  ground,  and  amalgamated.  These  two  operations 
are  carried  on  simultaneously  in  mills  containing  mercury.  The 
jamalgam  thus  formed  is  filtered  under  pressure,  then  distilled  in 
retorts,  the  mercury  being  driven  over  while  the  gold  remains  behind. 
The  non-amalgamated  portion  or  pulp  containing  an  appreciable 
amount  of  gold  is  treated  with  a  current  of  water;  then  it  passes  over 
porous -copper  amalgamating  plates  where  a  fresh  quantity  of  gold  is 
deposited.  The  pulp  is  then  concentrated,  yielding  what  is  called 
concentrates.  In  this  operation  two  classes  of  residues  are  obtained : 
The  heavy  residue,  called  tailings,  the  lighter,  called  slimes.  The 
tailings  and  the  slimes  are  important  residues,  reaching  60-70% 


THE  USE  OF  CYANOGEN  COMPOUNDS.         299 

of  the  mineral  at  the  Rand;  the  former  contains  7-10  grams  of  gold 
per  ton,  the  latter  4-7  grams. 

It  is  especially  these  residues  which  are  treated  with  potassium 
cyanide  in  order  to  extract  the  gold  left  from  the  amalgamation. 
However,  the  mineral  may  thus  be  treated  directly. 

Before  touching  upon  the  treatment  either  of  the  mineral,  the 
tailings,  slimes,  or  concentrate,  the  following  four  points  should  be 
carefully  brought  out  by  analyses  concerning  these  substances: 

(1)  The  gold-content,  so  as  to  know  the  amount  of  potassium 
cyanide  to  be  used. 

(2)  Whether  the  mineral  or  the  tailings  contains  the  gold  in  a 
finely  divided  state,  or  in  large  grains;  this  will  indicate  the  length 
of  treatment  with  the  cyanide  solution. 

(3)  Whether  the  mineral  on  the  tailings  be  acid  or  neutral. 

(4)  Whether  the  mineral  or  the  tailings  contain  an  appreciable 
quantity  of  metals  other  than  gold  and  silver,  having  some  affinity 
for  cyanogen. 

The  auriferous  materials  will  be  treated  according  as  they  have 
one  or  other  of  the  above  characteristics.  These  points  having  been 
clearly  established  the  treatment  of  minerals  or  tailings  may  be 
undertaken.  The  tailings  are  transferred  to  large  lixiviating  vats, 
sometimes  made  of  wood  or  brick  or  cement,  and  sometimes  of 
mortar,  and  rectangular  or  cylindrical  in  form,  whose  dimensions 
vary  according  to  the  works. 

At  the  works  of  the  African  Gold  Recovery  Company  where 
the  processes  of  McArthur  and  Forest  are  exploited,  the  vats  are 
wood,  cylindrical  in  shape,  13  meters  in  diameter  and  2.4  meters 
deep,  with  a  capacity  of  350  tons  of  mineral. 

The  Langlaate  Estale  Company  and  the  Block  Brick  Company 
use  circular  vats  of  brick  12  meters  in  diameter  and  3  meters  deep, 
containing  400  tons  of  mineral. 

At  the  works  of  the  Crown  Reef  Company  the  vats  are 
rectangular,  of  brick  and  cement,  12  meters  long,  11  meters  wide, 
3  meters  deep. 

The  vats  of  the  Durham-Rondepoort  Co.  and  of  the  Simmer 
and  Jack  Company  are  circular,  made  of  wood;  the  former  being 
12  meters  in  diameter  and  2.1  meters  deep;  the  latter  12.6  meters 
in  diameter  and  4.2  meters  in  height. 


300         THE  USE  OF  CYANOGEN  COMPOUNDS. 

At  Robinson's  works  smaller  circular  vats  are  in  use,  holding 
only  75  tons  of  mineral,  while  at  the  new  Primrose  works,  the  lixivi- 
ating vats  are  very  large  and  capable  of  holding  more  than  400  tons 
of  mineral. 

When  wooden  vats  are  used  it  is  customary  to  cover  the  inte- 
rior with  a  layer  of  paraffine  or  of  a  coal-tar  and  asphalt  compound, 
experience  having  shown  that  the  wood  retains  an  appreciable 
amount  of  gold. 

The  filtering-vats,  the  use  of  which  is  becoming  general,  are 
provided  with  a  false  bottom,  consisting  of  a  wooden  framework 
made  of  laths  covered  with  a  mat  of  cocoa  fibers,  or  a  double  mat 
of  jute,  or  a  layer  of  jute  and  one  of  coca  fiber,  and  sometimes  even 
with  quartz  fragments.  These  vats  are  also  provided  with  a  two- 
branched  drainage-pipe;  one  for  dilute  and  the  other  for  concen- 
trated solutions. 

Side  gates  or  sluices  are  used  in  discharging  the  mineral  after 
its  treatment  with  cyanide. 

First,  the  vats  are  filled  with  the  mineral  up  to  within  4  or  5  cc. 
of  the  top,  the  contents  carefully  leveled  and  the  cyanide  solution 
run  in.  This  solution  is  generally  prepared  by  dissolving  the  cyanide 
in  a  small  amount  of  water  in  a  small  wooden  vat,  and  then  dilu- 
ting this  solution  to  the  required  strength. 

When  acid  tailings  are  being  treated,  as  is  most  generally  the 
case,  the  neutral  minerals  having  been  almost  completely  used  up, 
they  should  first  be  washed  with  water  in  order  to  remove  the  soluble 
salts,  or  "  cyanicides  "  as  they  are  called.  This  washing  is  done 
economically  only  when  the  analysis  of  the  tailings  or  mineral  shows 
a  large  amount  of  soluble  salts.  In  some  works,  this  is  carried 
on  in  the  cyani ding- vats  themselves;  but  this  is  a  very  defective 
mode  of  treatment  for  these  vats  always  retain  on  their  walls  a 
certain  amount  of  cyanide,  arising  from  a  previous  operation;  this 
salt  dissolves  some  of  the  gold  and  as  these  wash-waters  are  rejected 
it  follows  that  there  is  a  loss  of  precious  metal.  It  is  therefore 
better  to  do  the  washing  in  special  vats,  after  which  the  mineral 
or  the  tailings  are  transferred  to  the  cyaniding-vats.  This  washing 
is  sometimes  followed  by  another,  this  time  using  a  caustic  soda 
solution,  containing  125  grams  per  1000  liters  of  water,  but  it  is 
generally  better  to  mix  the  acid  mineral  with  a  certain  amount  of 


THE  USE  OF  CYANOGEN  COMPOUNDS.  301 

powdered  lime  before  charging  the  cyaniding-vat,  the  amount  of  lime 
naturally  varying  with  the  quantity  of  cyanicides  present  in  the  min- 
eral (1  kg.  per  ton  of  very  acid  tailings  or  250  grams  per  ton  of  tailings 
just  from  the  battery).  This  method  is  more  economical  than  that  of 
caustic  soda;  lime  is  cheaper,  and  no  special  vat  is  necessary,  the  opera- 
tion being  carried  on  in  the  cyaniding-vats.  The  results  obtained  are 
also  better;  by  using  soda  the  charged  solutions  become  turbid  and 
befoul  the  zinc  which  later  is  to  be  used  for  the  precipitation  of  the 
gold,  whereas  with  lime  the  solutions  remain  perfectly  clear. 

When  the  mineral  has  been  washed  or  treated  with  lime  and 
been  transferred  to  the  cyaniding-vats,  the  cyanide  solution,  pre- 
pared as  above  stated,  is  added,  covering  the  materials.  The  amount 
should  be  about  one-third  of  the  weight  of  the  dry  matter.  This 
first  solution  is  called  "  strong  solution."  Its  strength  naturally 
varies  with  the  nature  of  the  mineral,  ranging  from  0.25-0.80%. 
In  the  case  of  ordinary  tailings  a  0.30%  "  strong  solution  "  is  used; 
for  acid  tailings  the  strength  of  the  solution  varies  from  0.25-0.50%. 
In  many  works  0.60-0.80%  solutions  are  used. 

It  should  be  mentioned  that  the  selective  action  of  cyanogen 
for  gold  grows  in  proportion  as  the  solution  is  less  concentrated; 
therefore  the  weaker  the  solution  the  less  foreign  metals  does  the 
cyanide  dissolve.  Therefore,  the  richer  in  heavy  metals  the  mineral 
is  the  weaker  the  solution  to  be  employed. 

The  length  of  the  treatment  also  varies,  from  12-24  hours,  accord- 
ing to  the  nature  of  the  mineral.  It  is  always  well  to  remove  a 
sample  of  the  liquid  from  time  to  time  in  order  to  make  sure  of 
an  artificial  diffusion.  In  the  case  of  minerals  which  require  several 
days'  treatment  it  is  best  to  remove  the  whole  of  the  solution  after 
24  hours,  and  to  add  a  fresh  solution.  And,  in  the  case  of  certain 
concentrates  requiring  several  weeks'  treatment,  the  cyanide  solu- 
tion should  be  renewed  every  2  to  3  days. 

When  the  cyanide  process  was  first  used  the  mineral  was  kept 
constantly  stirred  in  the  vats,  but  it  was  soon  found  out  that  if 
this  stirring  did  increase  the  yield  somewhat,  on  the  other  hand  the 
decomposition  of  the  cyanide  solution  was  hastened,  besides  entailing 
a  considerable  expense  in  motive  power.  Those  are  the  reasons  why 
this  modus  operandi  was  abandoned  and  in  its  place  the  percolation 
system  just  described  adopted. 


302  THE  USE  OF  CYANOGEN  COMPOUNDS 

By  taking  a  sample  of  the  solution  and  pouring  it  over  zinc  strips 
one  can  see  whether  the  contact  with  the  strong  cyanide  solution 
has  been  sufficient.  If  the  metal  grows  dull  the  lixiviation  is 
incomplete. 

When  the  lixiviation  is  sufficient  the  solution  is  transferred  to 
precipitation- vats  by  means  of  the  cock  and  the  pipe  used  in  re- 
moving strong  solutions,  then  a  fresh  cyanide  solution,  called  "weak 
solution,"  containing  only  0.15-0.40%  potassium  cyanide,  is  added 
to  the  mineral.  The  object  is  to  carry  away  the  gold  remaining 
from  the  preceding  treatment.  Only  half  as  much  solution  is  used 
as  in  the  first  treatment,  and  the  time  of  contact  is  only  one  to  two 
hours.  A  third  washing  is  made  with  the  "weak  solution'7  and 
a  fourth  washing  with  pure  water,  which  removes  the  last  portions  of 
the  charged  solution.  The  "weak  solutions"  are  withdrawn  by 
means  of  the  cock  and  the  tube  used  for  that  purpose  and  transferred 
to  zinc  boxes. 

At  the  Robinson  works  the  treatment  is  somewhat  different. 
The  solution  which  has  percolated  into  the  false  bottom  of  the  vat 
is  pumped  on  to  the  mineral  of  the  same  vat.  Thus  the  extraction 
is  more  complete,  and  the  amount  of  cyanide  solution  to  be  sub- 
jected to  the  action  of  zinc  being  smaller  the  losses  of  cyanides  are 
appreciably  reduced. 

Another  modification  consists  in  making  the  cyanide  solution, 
which  has  already  dissolved  some  precious  metal  in  the  first  vat, 
flow  from  this  first  vat  into  a  second,  and  then  into  a  third,  etc. 
The  cyanided  solutions  thus  obtained,  containing  more  gold,  give  a 
purer  precipitate  of  gold,  and  thus  the  losses  in  cyanide  are  likewise 
decreased. 

The  amount  of  cyanide  of  potassium  used  in  practice  for  the 
conversion  of  the  gold  to  the  form  of  gold-cyanide  is  always  much 
larger  than  that  required  theoretically.  Theoretically,  718  grams 
of  potassium  cyanide  are  necessary  in  order  to  dissolve  1  kg.  of 
metallic  gold;  but  in  practice,  in  order  to  dissolve  7  grams  of  gold, 
contained  in  1  ton  of  tailings,  350  grams  of  cyanide  are  required. 
That  is  a  minimum  seldom  attained,  except  in  special  cases  to  be 
Studied  later;  generally  500  grams  of  cyanide  are  used  per  ton  of 
tailings,  and  sometimes  this  amount  is  increased  to  700,  to  800  grams, 
and  even  to  900  grams  in  certain  cases. 


THE  USE  OF  CYANOGEN  COMPOUNDS.          303 

De  Mesenthal,  who  had  opportunity  to  study  the  cyaniding  proc- 
esses in  the  Transvaal  itself,  reports  that  for  1893  the  Robinson 
Company  used  on  an  average  625  grams.  In  1894  the  amount  of 
tailings  treated  at  the  Rand  amounted  to  1,200,000  tons,  requiring 
the  use  of  about  1200  of  cyanide,  or  about  1  kg.  of  cyanide  per  ton 
of  tailings. 

In  de  Wilde's  process  very  weak  cyanide  solutions  are  used  by 
means  of  a  system  of  circulation  and  filtration  which  allows  the  use  of 
only  105  grams  of  cyanide  per  ton  of  tailings  containing  15  grams  of 
gold.  Small  amounts  of  caustic  soda  are  added  now  and  then,  which 
facilitates  the  solution  of  gold  by  preventing  the  action  of  atmos- 
pheric agents,  carbonic  acid,  and  wa£er  from  causing  a  decomposi- 
tion of  the  cyanide.  In  order  to  obtain  perfect  results,  de  Wilde 
recommends  using  red  lead;  Moldenhauer,  using  ferrocyanide  of 
potassium;  Kendall,  sodium  peroxid. 

Finally,  two  very  similar  processes  for  dissolving  gold  in  potas- 
sium cyanide  will  be  mentioned.  The  results  which  they  pro- 
duce are  quite  vigorously  disputed,  and  yet  are  little  known.  These 
methods  certainly  require  a  careful  study,  till  now  they  have 
been  tried  only  in  few  cases  on  a  large  scale,  which  fact  does  not 
permit  of  their  being  judged  as  to  their  industrial  value.  These 
are  Sulman  and  Mulholland's  bromo-cyanide  mixed  processes. 

The  first  consists  in  adding  cyanogen  bromide  to  the  cyanide 
solution;  the  second  yields  the  cyanogen  bromide  during  the  reac- 
tion and  consists  in  simply  adding  bromine.  The  reaction  may  be 
thus  expressed: 

4Au  +  8KCN  +2Br2 +70  +H20 =4KAu(CN)2  +2KBr03  +2KOH, 
or  in  the  case  of  cyanogen  bromide, 

4  Au + 8KCN  +  30  +  H20 = 4K  Au(CN)  2  +  4KOH, 
4KAu(CN)2  +4CNBr  +4KOH  =4KCNAuBr  +4KCN  +2H20  +02. 

As  has  been  already  remarked,  the  halogen  acts  only  indirectly 
in  order  to  set  the  necessary  oxygen  free. 

According  to  Mulholland,  bromine  displaces  the  cyanogen  of  the 
cyanide,  which  being  set  free  reacts  on  gold,  forming  a  cyanide 
of  gold,  which  is  then  soluble  in  potassium  cyanide,  yielding  auro- 


304          THE  USE  OF  CYANOGEN  COMPOUNDS. 

cyanide.  Mulholland's  process  therefore  consists  in  forming  a 
gold  compound  more  soluble  in  potassium  cyanide  than  the  metal 
itself.  Bromine  should  not  be  in  excess,  otherwise  potassium  bromide 
and  free  hydrocyanic  acid  will  be  formed.  In  case  this  happens 
caustic  soda  or  lime  is  added.  Bromine  may  be  added  either  all 
at  one  time  or  in  small  portions;  the  amount  being  previously  deter- 
mined according  to  the  percentage  of  precious  metal  in  the  minerals. 
This  process  yields  97%  of  the  gold  with  the  use  of  a  smaller  quan- 
tity of  cyanide,  and  with  greater  ease  and  rapidity  of  solution. 

After  precipitation  with  zinc  the  bromine  may  then  be  recovered 
without  appreciable  loss. 

Such  are  the  chief  methods  used  in  carrying  on  the  first  part 
of  the  treatment  of  auriferous  minerals  by  the  cyanide  process. 
Finally,  as  has  been  seen  in  this  rapid  review,  these  methods  differ 
from  each  other  only  in  the  form  and  size  of  the  apparatus.  Never- 
theless, the  methods  have  not  yet  reached  perfection.  It  is  evi- 
dent that  the  amount  of  cyanogen  consumed  is  much  too  large, 
and  the  efforts  and  attention  of  chemists  and  manufacturers  of 
gold  districts  should  be  centered  on  this  point. 

It  now  remains  to  take  up  the  second  stage  of  the  cyaniding 
processes — that  is  the  precipitation  of  gold  from  the  cyanided  solu- 
tions. 

The  methods  are  quite  numerous,  and  will  be  taken  up  suc- 
cessively. These  processes  are  of  two  classes:  In  the  first  gold 
is  precipitated  by  metallic  zinc;  in  the  second  by  electrolysis.  There 
exist  other  special  processes,  but  they  have  had  but  few  trials. 

Precipitation  of  Gold  by  Means  of  Zinc. — The  type  of  these 
processes  is  that  of  Mac  Arthur  and  Forest.  This  is  based  on  the 
fact  that  zinc  displaces  gold  from  its  double  cyanide  as  follows: 

2KAu(CN)2 + Zn  =  K2Zn(CN)4 + Au2. 

The  zinc  should  have  a  special  shape;  as  sheets  the  surface 
to  be  acted  upon  is  too  small;  finely  or  coarsely  granulated,  or  in 
powder,  gives  very  unsatisfactory  results.  The  best  results  are 
obtained  with  zinc  in  the  form  of  shavings  freshly  prepared. 

These  shavings  are  so  prepared  that  they  present  a  large  sur- 
face. Thus  1  kg.  of  zinc  in  the  form  of  shavings  offers  a  surface 
of  more  than  8  square  meters. 


THE  USE  OF  CYANOGEN  COMPOUNDS.          305 

Pure  zinc  is  not  suitable;  only  commercial  zinc  should  be  used, 
;such  as  contains  some  lead,  which  with  the  zinc  forms  a  voltaic 
€ouple  which  facilitates  the  reaction. 

The  reaction  goes  on  quite  slowly  at  first,  but  just  as  soon  as 
the  gold  begins  to  become  deposited  on  the  zinc,  an  electric  couple, 
gold-zinc,  is  formed  which  greatly  aids  the  reaction;  but,  on  the 
other  hand,  the  gold-zinc  couple  decomposes  water  by  hydrolysis, 


20=Zn(OH2), 

the  zinc  hydrate  dissolving  in  the  excess  of  potassium  cyanide  solution, 
Zn(OH)2+4KCN=  K2Zn(CN)4+2KOH. 

This  is  one  reason  why  the  amount  of  zinc  used  much  exceeds  that 
indicated  by  the  general  reaction 

2KAu(CN)2  +  Zn  =  ZnK2(CN)4  +  2Au. 

On  the  other  hand,  the  alkali  produced  when  the  mineral  is 
neutralized,  or  from  the  cyanide  in  which  it  is  always  present,  and 
that  which  is  set  free  by  the  action  of  the  cyanide,  together  with  that 
formed  hi  the  reaction  between  zinc  hydrate  and  the  excess  of 
cyanide  —  all  this  alkali  dissolves  a  fresh  quantity  of  zinc,  according 
to  the  reaction 

Zn  +  2KOH=  Zn(OK)2  +  H2; 

potassium  zincate  acts  on  the  double  cyanide  of  zinc  and  potassium, 
Zn02K2  +  ZnK2Cy4  +  2H20  =  2ZnCy  2  +  4KOH, 

which  reaction  prevents  the  liquors  from  becoming  rich  in  zinc. 

In  the  presence  of  the  excess  of  cyanide  the  reaction  may  be  ex- 
pressed thus: 

4KCy  +  Zn  +  2H20=ZnK2Cy4+2KOH  +  H2. 

The  reaction  takes  place  as  above,  as  the  liberation  of  hydrogen 
may  be  noticed  in  the  zinc  boxes  during  the  precipitation.  Theo- 
retically this  hydrogen  should  have  a  reducing  action  on  the  double 


306          THE  USE  OF  CYANOGEN  COMPOUNDS. 

cyanide  of  gold  and  potassium,  setting  gold  free,  according  to  the 
reaction 

2KAu(CN)2  +  2H  =2CNH +2KCN +2Au. 

The  reaction  does  indeed  take  place  thus:  Potassium  cyanide  is 
formed  which  is  used  in  dissolving  a  fresh  amount  of  gold,  and  metallic 
gold  is  precipitated.  The  hydrocyanic  acid  set  free  in  the  above 
reaction,  coming  in  contact  with  the  solution  itself  with  an  excess  of 
potassa,  unites  with  it  in  order  to  form  potassium  cyanide, 

2CNH + 2KOH = 2CNK + 2H20. 

Finally,  the  liquor  should  necessarily  contain  an  excess  of  zinc, 
which  prevents  the  gold  from  redissolving  in  the  potassium  cyanide. 
Zinc  combined  with  potassium  has  a  greater  affinity  for  cyanogen 
than  gold  combined  with  potassium  has;  therefore,  when  a  solution 
of  potassium  cyanide  is  in  contact  with  zinc  it  will  not  dissolve 
the  precious  metal. 

The  precipitation  of  gold,  as  it  is  carried  on  at  the  works,  will 
now  be  taken  up. 

When  the  solution  of  potassium  aurocyanide  is  withdrawn  from 
the  lixiviation-vats  it  is  conducted  into  the  zinc  precipitation-vats, 
which  are  arranged  in  two  series.  One  contains  the  "  strong"  solu- 
tions, the  other  the  "weak"  solutions. 

These  vats  are  made  of  wood,  and  vary  in  size  according  to  the 
works.  As  a  rule,  they  are  6-8  meters  long,  0.6-1.25  meters  wide, 
and  0.7-0.8  meter  deep.  At  the  Robinson  Company's  works  they 
are  6.6x0.6X0.6  meters. 

They  are  slightly  inclined  lengthwise,  and  divided  into  com- 
partments 0.50-0.60  meter  long,  so  arranged  that  the  solution 
passes  from  one  compartment  into  another,  first  from  the  top,  then 
from  the  bottom.  In  these  compartments  are  small  boxes  or  troughs, 
the  bottom  of  whiih  is  a  sieve  made  of  iron  thread  60  meshes  per 
square  decimeter  and  fixed  on  a  movable  wooden  frame  fastened 
by  beams  several  centimeters  from  the  bottom  of  the  vat. 

In  these  troughs  are  placed  the  zinc  shavings  (about  18  kg. 
per  compartment).  At  the  head  of  the  box  a  compartment  is  left 
empty  in  order  that  the  slimes  which  may  come  from  the  lixiviation- 
vats  may  be  allowed  to  settle,  and  likewise  at  the  foot  a  double 


THE  USE  OF  CYANOGEN  COMPOUNDS.          307 

compartment  is  left  empty,  which  serves  to  hold  back  the  particles 
of  gold  carried  away  by  the  following  liquid  before  it  comes  to 
the  reservoirs. 

The  charged  solutions  are  allowed  to  flow  through  the  com- 
partments at  such  a  rate  that  in  9  hours  about  60  tons  of  auro- 
cyanide  solution,  representing  225  tons  of  mineral,  are  passed  through. 
In  this  way  the  loss  of  gold  by  being  carried  away  is  almost  noth- 
ing. Gold  is  precipitated  in  the  form  of  a  blackish  powder,  which 
falls  through  the  meshes  of  the  sieve  to  the  bottom  of  the  compart- 
ment. The  precipitation  is  generally  incomplete  if  on  emerging 
from  the  zinc  boxes  the  solution  contains  more  than  3  grams  of 
gold  per  ton,  in  which  case  the  operation  has  been  badly  con- 
ducted; on  the  other  hand,  if  it  does  not  contain  more  than  0.7 
gram  the  conditions  under  which  the  work  is  being  carried  on  are 
excellent. 

In  the  first  two  compartments  the  reaction  is  quite  vigorous; 
almost  all  of  the  gold  is  deposited;  zinc  is  rapidly  dissolved  and 
is  constantly  replaced  with  shavings  from  the  following  compart- 
ments so  that  the  last  of  these  is  always  filled  with  fresh  shavings. 

The  zinc  boxes  are  emptied  twice  a  month.  After  adding  water 
in  order  to  remove  the  charged  solution  the  sieves  are  withdrawn 
and  shaken  so  that  all  the  reduced  gold  which  adheres  to  the  meshes 
may  fall  to  the  bottom  of  the  vats.  The  whole  is  allowed  to  stand 
for  1  hour,  and  when  auriferous  slime  has  been  fully  precipitated 
the  clear  supernatant  liquid  is  siphoned  off  and  transferred  to  a 
reservoir. 

The  walls  of  the  vats  are  rinsed  with  pure  water,  and  the  mix- 
ture of  water,  gold,  and  pulverulent  zinc  is  thrown  on  to  a  sieve, 
16  meshes  per  square  cc.  The  mixture  is  stirred  with  a  stick,  the 
end  of  which  is  of  rubber.  In  this  way  the  zinc  remains  on  the 
sieve  while  the  slime  containing  gold,  silver,  zinc,  lead,  tin,  anti- 
mony, etc.,  passes  through.  This  slime  is  allowed  to  settle  in  a 
small  vat,  placed  under  the  sieve,  then  dried  in  shallow  pans. 

On  the  other  hand,  the  zinc  clippings  which  remain  on  the  grating 
are  washed  and  rubbed  under  water  so  as  to  remove  as  much  as 
possible  the  gold  which  adheres  to  them.  The  grates  are  likewise 
brushed  under  water.  After  settling  the  water  is  decanted  and 
the  mud  is  added  to  that  of  the  compartments. 


308  THE  USE  OF  CYANOGEN  COMPOUNDS. 

In  certain  works  zinc  boxes  are  used,  fitted  up  with  a  longi- 
tudinal washer  situated  on  the  side  of  the  boxes  and  communi- 
cating with  each  one  of  the  compartments  by  openings  ending  below 
the  grating.  These  openings,  closed  with  a  plug  during  precipita- 
tion, are  used  in  allowing  the  auriferous  slime  to  pass  into  the  washer; 
the  slime  falls  upon  a  filter  where  it  is  afterwards  collected.  Gener- 
ally the  zinc  boxes  are  covered  with  strong  iron  gratings  which 
may  be  locked  with  a  key.  The  auriferous  slimes  thus  collected 
contain  a  large  amount  of  zinc  and  of  lead,  some  silver  and  copper, 
traces  of  antimony,  arsenic,  nickel,  cobalt,  aluminum,  ferrocyanide 
of  potassium  and  of  zinc,  cyanide  of  potassium  and  of  zinc,  cyanide 
of  iron,  sulphide  of  iron,  carbonates  of  potash  and  lime,  iron  oxid, 
silica,  etc.  These  are  dried  in  shajlow  pans,  then  they  are  roasted 
in  order  to  oxidize  the  metals  and  to  decompose  the  cyanides. 

This  roasting  takes  place  in  small  muffled  furnaces  on  cast-iron 
dishes  and  at  a  dull-red 'heat,  a  temperature  which  should  not  be 
exceeded,  the  mass  being  gently  stirred  so  as  to  avoid  any  loss  of 
gold  dust  which  is  very  fine.  During  this  operation  carbonic  acid 
and  ammonia  proceeding  from  the  decomposition  of  the  cyanides 
are  set  free.  In  order  to  oxidize  the  zinc  more  easily  it  is  advised 
to  add  2-3%  of  potassium  nitrate  before  the  roasting.  There 
is  thus  formed  potassium  zincate  which  is  less  easily  reduced  than 
the  oxid  of  zinc. 

The  roasted  mass  is  then  fused  in  the  following  way: 

An  intimate  mixture  is  made  of  the  very  dry  auriferous  pre- 
cipitate wish  sodium  carbonate  or  bicarbonate,  borax,  sand  or 
fluorspar,  in  the  following  proportions: 

(I)  Roasted  auriferous  slime 820  parts 

Carbonate  of  sodium 85    "'.  • 

Borax 55    ": 

Fluorspar 40    '1 

1000    ": 
Or 

(II)  Roasted  auriferous  slime 100    'r 

Bicarbonate  of  sodium 50    "'. 

Borax 25    " 

Sand..  10  .": 


THE  USE  OF  CYANOGEN  COMPOUNDS.          309 

This  mixture  is  placed  in  plumbago  crucibles  which  are  three 
quarters  filled,  and  these  are  placed  in  a  series  of  three  in  fusion 
furnaces.  The  mass  fuses  quite  rapidly,  a  very  fluid  scoria  being 
formed  which  acts  on  the  crucibles  to  such  an  extent  that  they 
are  soon  out  of  order.  As  a  rule  they  may  be  used  for  no  more 
than  six  fusions.  When  the  mass  has  reached  the  state  of  quiet 
fusion  the  crucibles  are  removed  from  the  furnaces,  and  their  con- 
tents poured  into  conical-shaped  ingot  moulds  which  have  been 
previously  rubbed  with  chalk  so  as  to  prevent  the  slag  from 
adhering. 

The  metallic  portion  being  heavier  falls  to  the  bottom;  after 
cooling  the  ingots  are  broken  and  thus  the  metallic  bottom  may 
be  separated  from  the  dross. 

The  gold  thus  obtained  averages  650  to  800  thousandths;  it 
always  contains  zinc,  lead,  copper,  and  silver  in  variable  amounts. 
Often  the  product  from  many  of  these  operations  is  again  fused  with 
borax  at  as  low  a  temperature  as  possible. 

Such,  in  a  general  way,  is  the  process  of  Mac  Arthur  and  Forest. 
Moreover,  it  differs  from  the  others  only  in  the  method  of  precipita- 
tion, the  cyaniding  being  done  practically  in  the  same  manner  in 
all  the  methods.  As  has  been  seen,  in  the  precipitation  by  means 
of  zinc  there  is  formed  potassium-zinc-cyanide,  which  involves  an 
enormous  consumption  of  potassium  cyanide.  In  order  to  do  away 
with  this  objection  various  methods  have  been  proposed,  the  object 
being  especially  to  recover  the  potassium  cyanide  which  is  partially 
lost  in  Mac  Arthur  and  Forest's  process. 

Andre,  chemist  of  the  Deutsche  Gold  and  Silber  Scheide  Anstalt 
at  Frankfort,  proposed  the  use  of  aluminum  instead  of  zinc,  in  which 
case  the  reaction  is  as  follows: 

6K  AuCy  2 + 6KOH  +  2A1=  6Au  +  12KCN + A1203  +  3H20. 

As  is  seen,  the  cyanide  is  in  this  way  wholly  reproduced,  and 
on  the  other  hand  there  is  formed  a  precipitate  of  gold  and  alumina, 
the  separation  of  which  is  rather  easy. 

That  is  of  an  immense  advantage,  and  Andre's  process  would 
certainly  be  adaptable  to  trial  on  a  large  scale  if  the  cost  of 
aluminium  were  not  so  great. 


310          THE  USE  OF  CYANOGEN  COMPOUNDS. 

Molloy's  process  consists  in  using  a  sodium  amalgam  according 
to  the  reaction 

HgNa + KAuCy2=  HgAu  +  KCy  +  NaCy . 

The  charged  solution  passes  through  a  vat  containing  mercury, 
at  the  surface  of  which  is  placed  a  vertical  cylinder  containing  a 
solution  of  sodium  carbonate,  and  dipping  slightly  in  the  mercury 
bath.  A  sheet  of  lead  dips  into  this  solution.  The  mercury  and 
the  lead  thus  form  two  electrodes,  united  to  the  two  holes  of  a  bat- 
tery. Under  the  influence  of  the  electric  current  sodium  is  formed, 

C03Na2=C02  +  0  +  Na2, 

which  unites  with  mercury,  forming  an  amalgam,  which  latter  decom- 
poses the  aurocyanide  solution  yielding  a  gold  amalgam  and  a  solu- 
tion of  sodium  and  potassium  cyanide  better  suited  to  dissolve 
a  fresh  amount  of  gold.  Molloy's  process  is  not  yet  much  in  use, 
and  the  results  produced  by  it  are  much  questioned.  However, 
this  process  deserves  to  be  kept  in  mind. 

In  1894  Johnstone  proposed  making  the  potassium-aurocyanide 
solution  flow  on  wood  charcoal,  which  is  afterward  burned  in  order 
to  extract  the  precious  metal.  At  present  no  judgment  can  be 
rendered  as  to  the  value  of  this  process,  which,  however,  seems  to 
present  certain  advantages  worthy  of  consideration. 

Among  the  chemical  precipitation  processes  worthy  of  attention 
that  invented  by  de  Wilde  should  be  cited.  It  consists  of  three 
stages : 

(1)  Solution  of  the  gold  by  means  of  potassium  cyanide. 

(2)  Recovery  of  the  excess  of  potassium  cyanide. 

(3)  Precipitation  of  the  gold. 

The  first  operation,  or  the  cyaniding  of  the  mineral,  is  carried 
on  in  the  same  way  as  in  Mac  Arthur  and  Forest's  process,  with 
this  exception  (it  has  already  been  mentioned  in  the  first  part  of 
this  chapter),  that  in  this  case  much  weaker  solutions  of  cyanide 
are  used,  for  it  is  no  longer  necessary  to  use  relatively  strong  solu- 
tions in  order  to  avoid  the  incomplete  precipitation  by  the  zinc. 

When  the  gold   has   been  dissolved  in  the  cyanide  the  recovery 


THE  USE  OF  CYANOGEN  COMPOUNDS.          311 

of  the  excess  of  cyanide  is  immediately  taken  up.  To  do  this 
ferrous  sulphate  is  added  to  the  solution,  small  portions  at  a  time, 
with  constant  stirring.  There  is  formed  a  precipitate,  which  at 
first  is  yellowish  red  but  later  becomes  green,  which  is  a  double 
cyanide  of  iron  and  potassium,  Fe2K(CN)3,  the  reaction  being  as 
follows : 

2S04Fe +5KCN =2S04K2  +Fe2K(CN)3. 

The  precipitate  is  separated  by  means  of  a  filter-press,  and 
allowed  to  stand  in  air,  where  it  becomes  rapidly  converted  into 
Prussian  blue,  [Fe(CN)6]6(Fe2)2;  this  Prussian  blue  is  then  treated 
with  a  strong  caustic  potash  solution,  and  is  converted  into  iron- 
hydrate  and  potassium  ferrocyanide, 

(FeCy6)3(Fe2)2  +  12KOH =3Fe(CN)6K4 +2Fe2(OH)6. 

The  iron  hydrate  is  filtered,  the  ferrocyanide  filtrate  being  con- 
verted into  cyanide  by  the  ordinary  methods. 

The  ferrous  sulphate  should  be  added  in  slight  excess,  other- 
wise it  would  be  detrimental.  This  is  controlled  by  adding  a  few 
drops  of  ferri cyanide  to  the  solution,  and  when  this  solution  is  colored 
blue,  enough  ferrous  sulphate  has  been  added. 

Before  adding  the  ferrous  sulphate  the  alkalinity  of  the  solu- 
tion should  be  determined.  It  should  be  scarcely  sufficient  to  turn 
litmus  paper,  for  if  it  be  too  alkaline  the  addition  of  ferrous  sul- 
phate will  cause  a  precipitation  of  ferrous  hydrate  which  would 
remove  part  of  the  gold. 

The  precipitation  of  gold  by  de  Wilde's  process  is  based  on  the 
fact  that  if  a  solution  of  copper  sulphate  be  added  to  the  potassium 
aurocyanide  solution,  acidified  with  sulphurous  acid,  the  potassium 
aurocyanide  will  be  decomposed  with  formation  of  gold  cyanide 
and  copper  cyanide,  which  are  precipitated,  as  in  the  reaction 

2KAu(CN)2+S04Cu=S04K2+2AuCN+Cu(CN). 

The  cuprous  cyanide  results  from  the  action  of  sulphurous  acid 
on  cupric  cyanide,  Cu(CN)2,  which  is  first  formed  so  that  the  follow- 
ing is  obtained: 

2Cu(CN)2+S03H2=2CNH+S03+Cu2(CN)2. 


312  THE  USE  OF  CYANOGEN  COMPOUNDS. 

Either  sulphurous  acid  may  be  used,  or  an  alkaline  bisulphite; 
this  is  added  until  a  slightly  acid  reaction  is  perceptible. 

The  copper  sulphate  should  be  added  in  slight  excess  if  a  com- 
plete precipitation  is  desired.  The  point  of  excess  may  be  deter- 
mined by  testing  with  potassium  ferrocyanide,  which  with  a  cop- 
per salt  gives  a  red  precipitate  of  cupric  ferrocyanide. 

The  operation  is  carried  on  in  large  vats.  The  whole  is  allowed 
to  stand  for  10-12  hours,  then  the  solution  is  decanted  through 
the  cocks,  and  the  precipitate  washed  and  dried. 

It  is  then  ignited  in  order  to  convert  the  aurous  cyanide  into 
metallic  gold  and  the  cuprous  cyanide  into  copper  oxid, 

AuCy + Cu2Cy  2 + 2  0  =  Au  -f 2CuO + 3CN. 

The  ignited  product  is  then  heated  with  sulphuric  acid  60°  B.,  which 
dissolves  the  copper,  leaving  the  gold  behind: 

Au +2CuO  +2S04H2  =2S04Cu  +  Au+2H20. 

The  copper  sulphate  is  thus  recovered. 

De  Wilde's  process  has  been  applied  with  success  in  the  Trans- 
vaal" gold  districts  by  Loevy,  and  the  results  obtained  have  been 
in  all  points  satisfactory,  not  only  from  the  standpoint  of 
economy  but  also  from  the  completeness  of  the  extraction.  The 
following  are  some  of  its  advantages: 

(1)  Very  much    less    consumption  of  potassium  cyanide  (5  or 
6  times  less  than  in  Mac  Arthur  and  Forest's  process). 

(2)  The   almost  complete  recovery  of  the  excess  of  potassium 
.cyanides. 

(3)  Likewise  the  almost  complete  recovery  of  the  precipitating 
•agent.     These  advantages  the  MacArthur  process  does  not  possess. 

Besides  these  methods,  which  are  based  on  purely  chemical  reac- 
tions, are  processes  based  on  the  use  of  electricity  as  a  means  of 
precipitating  the  gold. 

To  Siemens  and  Halske  of  Berlin  belong  the  honor  of  having 
.applied  electrolysis  to  the  extraction  of  gold  from  charged  solutions. 

In  1887  Siemens  noticed  that  the  gold  anodes  used  in  his  electro- 
plating works  at  Berlin  lost  in  weight  when  they  were  left  in  the 


THE  USE  OF  CYANOGEN  COMPOUNDS.          313 

charged  solution  after  the  current  was  cut  off.  This  phenomenon 
attracted  the  attention  of  the  celebrated  electrometallurgist,  who* 
is  justly  called  the  pioneer  of  electrolysis,  and  he  immediately  sought 
to  profit  by  it. 

In  1888  the  first  works  for  the  treatment  of  auriferous  solutions 
by  electrolysis  were  established  at  Siebenburgen,  and  in  1889  other 
works  were  set  up  successively  in  Hungary,  Siberia,  and  in  America. 
At  the  present  time  Siemens  and  Halske's  process  is  in  regular  opera- 
tion at  the  Worcester  mines  (in  the  Rand  district)  belonging  to  the 
Rand  Central  Ore  Reduction  Company,  Limited.  It  is  carried  on 
in  this  way: 

The  gold  is  dissolved  by  the  aid  of  strong  cyanide  solutions 
0.06-0.08%  and  weak  cyanide  solutions  0.01%,  in  five  large  vats 
having  a  capacity  of  75  cubic  meters. 

The  precipitation  takes  place  in  four  vats,  whose  dimensions 
are  6x2.4x1.2  meters.  The  anodes  are  iron  plates  3  mm.  in 
thickness,  2.1  meters  long,  and  0.9  meters  wide,  dipping  in  the 
potassium-gold-cyanide  solution,  and  held  in  a  vertical  position  by 
means  of  pieces  of  wood  placed  on  the  bottom  and  on  the  lateral 
walls  of  the  vats.  One  half  of  the  anode  dips  to  the  bottom  of  the 
vat,  while  the  other  goes  down  to  only  2.5  cm.  from  the  bottom. 
In  this  way  the  vats  are  divided  into  a  series  of  compartments 
between  which  the  liquid  flows  alternately  from  down  up  and  from 
up  down.  The  anodes  are  covered  with  cloth  so  as  to  prevent  short 
circuiting. 

The  cathodes  are  thin  lead  sheets.  They  are  placed  between  the 
anodes  and  fixed  on  wooden  frames  which  may  be  easily  raised. 
The  vats  are  covered  with  a  cover  locked  with  a  key,  and  are  opened 
only  to  collect  the  gold. 

The  electric  current  is  furnished  by  a  Siemens  dynamo  of  8  volts 
and  600  amperes;  it  is  6  volts  and  10  amperes  per  ton  of  mineral. 
Above  6  volts  the  cyanide  is  much  decomposed. 

The  gold  is  collected  once  a  month.  The  vats  are  opened,  and 
one  by  one  the  wooden  frames  supporting  the  lead  sheets  are 
removed  and  replaced  by  new  ones.  This  requires  but  very  little 
time,  which  is  of  great  advantage  as  no  interruption  of  work  is  neces- 
sary. The  lead  sheets  upon  which  an  adhering  deposit  of  gold  is 
formed,  amounting  from  2-12%,  are  melted  and  cupelled. 


314  THE  USE    OF  CYANOGEN  COMPOUNDS. 

During  the  precipitation  of  gold  the  iron  anodes  are  attacked 
by  the  potassium  cyanide,  forming  potassium  ferrocyanide,  which, 
reacting  on  oxid  of  iron  formed,  yields  Prussian  blue,  and  this  is 
precipitated  on  the  anode,  thanks  to  a  special  coating  with  which 
this  is  covered.  It  is  collected  and  treated  as  usual  in  order  to  con- 
vert it  again  into  cyanide. 

Siemens  and  Halske's  process  fulfils  the  conditions  stated  by 
de  Germet  in  his  paper  before  the  Chemical  and  Metallurg- 
ical Society  of  South  Africa,  which  conditions  may  thus  be  re- 
viewed: 

(1)  The  cathodes  should  be  of  a  metal  to  which  gold  sufficiently 
adheres. 

(2)  This  metal  should  be  capable  of  being  drawn  out  into  thin 
sheets  in  order  that  the  weight  may  be  as  small  as  possible. 

(3)  It  should  be  easy  to  remove  the  gold  from  it. 

(4)  The  cathodes  should  not  be  more  electropositive  than  the 
anodes,  so  as  to  avoid  the  production  of  reverse  currents  when  the 
current  is  shut  off. 

Siemens  and  Halske's  process  has  been  much  criticized,  and 
different  inventors  have  modified  it  in  various  ways. 

First  is  Keith's  process  (1895),  in  which  the  lixiviation  is  carried 
on  with  0.01-0.5%  solutions  of  cyanide,  to  which  has  been  added 
double  cyanide  of  mercury  and  potassium  60-300  grams  per  ton 
of  solution.  Gold,  an  electropositive  element  when  considered  in 
relation  to  mercury,  decomposes  the  cyanide  of  this  metal,  setting 
cyanogen  and  mercury  free.  The  latter  unites  with  gold,  forming 
an  amalgam,  but  under  the  action  of  the  voltaic  couple  gold  is  dis- 
solved and  the  thin  film  of  mercury  also  dissolves  in  the  cyanide, 
in  order  to  reproduce  the  double  cyanide,  which  may  then  act  indefi- 
nitely. In  practice,  the  operation  is  carried  on  as  follows:  On 
issuing  from  the  lixiviation-vats  the  liquor  passes  into  wooden 
boxes  containing  copper  plates  used  as  cathodes  and  arranged  as 
in 'Siemens'  process.  Between  these  copper  plates  are  placed  por- 
ous jars  containing  a  solution  of  ammonium  chloride  or  sulphate, 
into  which  iron  or  zinc  rods  dip,  these  used  as  anodes.  Under 
the  action  of  the  current,  whose  electromotive  force  is  about  one 
volt,^  mercury  is  deposited  upon  the  copper  plates,  and  it  is  upon 
these  amalgamated  plates  that  gold  is  later  deposited.  They  are 


THE  USE  OF  CYANOGEN  COMPOUNDS.          315 

cleaned  at  regular  intervals  and  without  interruption,  as  in  the  Sie- 
mens process. 

Not  having  yet  been  tried  on  an  industrial  scale  it  is  impos- 
sible to  judge  of  the  value  of  this  process.  Nevertheless  its  inven- 
tor claims  as  advantages: 

(1)  The  cyanide  is  not  oxidized  into  cyanate. 

(2)  Mercury  facilitates  the  precipitation  of  gold. 

In  Pfleges'  process,  likewise  dating  from  1895,  the  electrode  on 
which  the  gold  is  deposited  consists  of  metallic  nettings  sepa- 
rated about  1J-3  mm.  and  of  about  one  thread  per  millimeter, 
presenting  therefore  a  very  large  surface.  The  bath  around  the 
diaphragms  consists  of  a  5%  caustic  soda  solution,  and  includes 
zinc  sheets,  which  with  the  netting  form  a  sort  of  Daniell  pile.  The 
bath  is  divided  by  partitions  which  make  it  necessary  for  the  soda 
solution  to  circulate  in  such  a  manner  that  the  points  of  contact 
with  the  netting  are  increased.  According  to  the  author,  the  entire 
efficiency  of  the  process  is  due  to  the  great  extent  of  surfaces  which 
the  metallic  nettings  offer  for  the  deposit  of  gold. 

Finally,  may  be  mentioned  the  method  of  Andreoli  in  1897, 
and  which  is  only  a  modification  of  Siemens'  process,  the  used  oxi- 
dized lead  anodes,  which,  it  seems,  are  entirely  resistent.  These 
anodes  are  obtained  by  placing  sheets  of  lead  into  sodium  plum- 
bate,  washing  them,  and  then  plunging  them  into  a  solution  of 
potassium  cyanide,  where,  under  the  action  of  a  strong  current 
they  become  covered  with  a  thin  film  of  lead  peroxide. 

The  cathodes  are  of  iron,  and  gold  deposits  on  them  in  a  closely 
adhering  form.  When  the  deposit  of  the  precious  metal  is  deemed 
sufficient,  the  cathodes  are  withdrawn  and  plunged  into  melted 
lead,  into  which  the  gold  dissolves,  and  when  the  gold  content  of 
the  alloy  thus  formed  is  high  enough  it  is  cupelled.  By  the  use 
of  oxidized  lead  anodes  the  formation  of  ferric  compounds,  which 
complicate  electrolysis,  is  avoided. 

The  yield  and  the  net  cost  of  these  processes  vary  much  accord- 
ing to  the  works  and  the  nature  of  the  minerals  treated. 

Nevertheless  in  the  Transvaal  it  is  generally  estimated  that  the 
MacArthur  and  Forest  process  gives  an  average  extraction  of  70 
to  75%,  the  net  cost  of  treating  one  ton  of  tailings  by  this  method 
being  valued  at  from  8  to  9  francs. 


316          THE  USE  OF  CYANOGEN  COMPOUNDS. 

By  Siemens'  process,  the  average  extraction  is  70%,  requiring 
113  grams  of  potassium  cyanide  per  ton  of  tailings.  The  total 
expenses  are  only  3.75  francs  per  ton,  and  even  3.1  francs  in  some 
cases. 

Among  the  other  uses  of  potassium  cyanide  must  be  mentioned 
gold  and  silver  electroplating.  The  objects,  burnished  and  scoured, 
are  placed  in  a  bath  containing  1  gram  gold  chloride  or  silver  cyanider 
according  as  it  is  gold-  or  silver-plating,  and  10  grams  of  potassium 
cyanide  dissolved  in  450  grams  of  water.  A  gold  or  silver  sheet  is 
suspended  at  the  positive  electrode;  it  dissolves  just  as  fast  as  the 
gold  or  silver  of  the  bath  is  deposited  on  the  objects  placed  at  the 
negative  pole,  and  thus  the  bath  is  kept  constantly  at  the  same  degree 
of  concentration. 

It  is  also  used  sometimes  in  reducing  metallic  oxides. 

It  may  be  used  in  cleaning  silverware  which  has  become  yellow- 
ish. A  good  formula  for  this  purpose  is  the  following: 

Distilled  water 1000  parts 

Potassium  cyanide 30      " 

Hyposulphite  of  soda 20      " 

Ammonia — a  sufficient  quantity  to  give  a  decided  alkaline 
reaction. 

Potassium  cyanide  was  for  some  time  used  in  photography,  for 
fixing  the  negatives,  on  account  of  its  property  or  dissolving  gold 
and  silver.  It  is  now  replaced  by  sodium  hyposulphite,  which  has 
the  great  advantage  of  not  being  poisonous. 

It  is  used  in  the  preparation  of  soluble  garnet  (potassium  iso- 
purpurate)  with  picric  acid,  and  in  the  preparation  of  cresylpurpuric 
acid  with  trinitrocresylic  acid. 

It  is  recommended  in  medicine  for  combatting  neurajgia  and 
megrims  (Trousseau).  It  is  given  in  0.50%  lotions. 

Among  the  other  cyanides  sometimes  used  may  be  mentioned 
zinc  cyanide,  which  is  used  in  therapeutics  as  an  antispasmodic;, 
silver  cyanide  used  in  silver  electroplating,  and  mercury  cyanide 
recommended  as  an  antisyphilitic. 

Ferrocyanides.  —  Potassium  ferrocyanide  is  quite  extensively 
used. 


THE  USE  OF  CYANOGEN  COMPOUNDS.          317 

A  large  portion  (50%)  of  the  ferrocyanide  produced  is  used  in 
the  manufacture  of  potassium  cyanide.  The  remainder  is  used  in 
various  ways  in  the  arts  and  trades.  It  is  used  in  the  preparation 
of  potassium  ferrocyanide  and  of  Prussian  blue. 

It  is  employed  in  dyeing,  where  it  is  used  in  coloring  blue  and 
in  weighting.  It  is  frequently  used  in  dyeing  silk  black  with  the 
aid  of  logwood  and  with  aniline  black.  It  is  also  much  used  in 
the  production  of  steam  colors.  Of  this  Lyon  consumes  about  300 
tons  annually. 

Ferrocyanide  of  tin,  obtained  by  double  decomposition  of  a 
tin  salt  and  potassium  ferrocyanide,  finds  quite  extensive  use  in 
dyeing,  in  the  production  of  white  discharges  as  substantive  colors, 
and  in  the  production  of  certain  steam  colors  added  to  the  blues. 

The  cementation  of  certain  special  steel  (springs,  tools,  etc.), 
also  requires  the  use  of  some  ferrocyanide.  In  this  respect  we 
must  mention  the  remarkable  role  which  the  cyanides  play  in  cemen- 
tation. 

In  1850,  Caron  demonstrated  to  the  Academic  des  Sciences 
that  the  steeling  substance  in  cementation  was  an  alkali  cyanide 
formed  by  the  carbon  used,  the  alkali  contained  in  the  ashes  of  this 
carbon  and  atmospheric  nitrogen.  By  a  remarkable  series  of  ex- 
periments Caron  proved  that  carbon  without  alkali  or  without 
nitrogen  could  not  produce  cementation,  and  that  cementation  was 
due  to  the  formation  of  an  alkali  cyanide,  an  hypothesis  confirmed 
by  the  fact  that  lime,  which  does  not  yield  cyanide  at  the  tempera- 
ture of  cementation,  does  not  produce  this  phenomenon.  From  this; 
Caron  concludes  that  the  most  favorable  conditions  for  a  good 
cementation  are  those  which  permit  the  formation  of  cyanides. 

The  cement,  therefore,  probably  owes  its  activity  to  alkali  or 
alkaline-earth  cyanides  which  are  formed  during  cementation,  and 
if  these  cyanides  are  not  the  sole  agents  of  the  cementation  they 
are,  at  least,  the  most  important.  But  in  all  probability  (experi- 
ment demonstrates  this)  they  do  not  act  because  of  the  nitrogen 
which  they  contain,  but  simply  as  carriers  of  carbon.  This  property 
which  the  cyanides  possess  is  due  to  a  certain  fixedness  which  does 
not  permit  them  to  give  up  their  carbon  except  at  the  temperature 
at  which  cementation  takes  place. 

In  certain  works  cementation  is  still   superficially  and  rapidly 


318         THE  USE  OF  CYANOGEN  COMPOUNDS. 

done  by  means  of  wood-charcoal.  Reaumur  recommended  as  an 
excellent  cement  a  mixture  of  wood-charcoal  and  sea-salt.  Deep 
•cementations  are  obtained  with  a  mixture  of  3  parts  charcoal  and 
1  part  barium  carbonate  (barium  cyanide  being  less  volatile  allows 
operating  at  a  higher  temperature,  and  for  this  purpose  it  is  par- 
ticularly recommended  by  Margueritte  and  Sourdeval  and  Caron). 
Potassium  ferrocyanide  enters  into  the  composition  of  a  very 
explosive  powder,  the  so-called  white  gun-powder,  exploding  by 
concussion  or  ignition.  This  powder  was  invented  by  Augendre, 
and  was  made  of  the  following  substances: 

Prussiate  of  potash 1  part 

Chlorate  of  potash 2  parts 

Sugar 1  part 

Pole  has  improved  this  powder  and  gives  it  the  following  com- 
position : 

Prussiate  of  potash 28  parts 

Chlorate  of  potash 49   " 

Sugar 23    " 

Its  advantages  over  ordinary  powder  are: 

(1)  It  is  not  hygrometric,  and  keeps  better  than  ordinary  powder. 

(2)  It  produces  more  gas  and  leaves  less  residue  than  black 
powder,  which  leaves  68%  solid  residue,  while  the  white  powder 
leaves  only  31  %„    The  gas  produced  consists  of  a  mixture  of  nitro- 
gen, carbon  monoxide,  carbonic  acid,  and  water-vapor.     The  residue 
is  composed  of  cyanide  and  chloride  of  potassium  and  a  little  iron 
carbide. 

(3)  Its  mechanical  effect  is  a  little  greater.    On  the  other  hand, 
it  has  the  serious  objection  of  strongly  oxidizing  iron  cannon,  and 
at  present  it  is  scarcely  used. 

Ferrocyanide  powder  is  very  sensitive  to  the  electric  spark. 

Potassium  ferrocyanide  is  still  sometimes  used  in  therapeutics 
as  a  diuretic.  It  was  formerly  used  as  an  antifebril,  mixed  with 
urea,  but  to-day  it  has  fallen  into  complete  disuse. 

Finally,  potassium  ferrocyanide  is  a  very  important  and  much 
used  reagent  in  all  laboratories. 


THE  USE  OF  CYANOGEN  COMPOUNDS.          319 

Ferricyanide. — Red  prussiate  of  potash  is  quite  frequently 
utilized  in  dyeing  and  in  printing,  because  of  its  very  energetic 
oxdizing  properties. 

It  is  used  in  the  production  of  aniline  black  and  violet.  It 
converts  aniline  into  Perkins'  violet.  It  is  likewise  used  in  the 
production  of  steam  colors  direct  from  wood  (logwood,  Lima  wood, 
Pernambuco  wood,  Brazilian  wood) ;  it  gives  either  darker  shades 
or  converted  print  colors,  puces,  reds,  violets.  It  has  the  advan- 
tage of  not  attacking  the  steel  doctors,  and  does  not  copper  the 
colors  as  do  the  copper  salts. 

The  printing  of  calicoes  employs  large  quantities  as  discharges. 
Mixed  with  a  soda  or  potash  solution  (Mercer  liquor)  it  is  used  in 
producing  white  patterns  on  fabrics  dyed  in  indigo  blue.  Likewise 
a  mixture  of  nitrate  of  lead  and  potassium  ferricyanide  is  a  very 
powerful  corroding  agent.  Finally,  it  is  used  in  manufacturing 
special  papers  for  photography  and  blue-prints. 

Prussian  Blue — This  compound,  which  formerly  was  utilized 
to  a  great  extent,  is  not  much  used  to-day.  The  discovery  of  arti- 
ficial blues  has  completely  dethroned  it,  and  moreover  the  colors 
which  it  gives  on  fabrics,  although  they  are  fixed  enough  even  on 
contact  with  acids,  are,  however,  objectionable  because  they  are 
not  resistant  to  soap,  and  especially  to  alkalis. 

Coloring  with  Prussian  blue  is  always  obtained  by  the  direct 
formation  of  the  coloring  substance  on  the  fabric,  by  first  fixing 
ferric  hydrate  on  the  fabric  and  then  passing  through  a  potassium 
ferrocyanide  bath  acidified  with  a  mineral  acid. 

Prepared  Prussian  blue  is  used  in  oil-painting,  in  the  bluing 
and  printing  of  papers  and  calicoes,  and  at  present  is  especially 
used  as  a  plastic  color. 

Sulphocyanides. — Sulphocyanide  of  potassium  as  such  has  no 
place  in  the  arts  and  trades.  It  is  especially  used  in  the  preparation 
of  sulphocyanides  of  tin,  aluminium,  and  copper,  which  are  more 
or  less  used.  Aluminium  sulphocyanide  is  sometimes  used  instead 
of  the  acetate  in  printing  steam  reds  and  pinks.  Not  being  acid 
as  is  aluminium  acetate,  it  has  the  advantage  over  the  latter  of  not 
attacking  the  steel  doctors,  and  moreover  of  giving  clearer  and 
more  brilliant  reds  than  those  of  the  acetate.  Some  tunes  sulpho- 


320          THE  USE  OF  CYANOGEN  COMPOUNDS. 

cyanide  of  potassium  is  mixed  with  colors  in  order  to  avoid  attack- 
ing, the  doctors. 

Tin  sulphocyanide,  which  is  obtained  by  double  decomposition  of 
a  commercial  tin  salt  with  ammonium  sulphocyanide,  is  quite  often 
used  in  printing  cotton  as  acid  discharges  on  direct  colors. 

The  canarine,  a  yellow  color  which  is  no  longer  used,  is  nothing 
more  than  persulphocyanogen,  produced  by  the  oxidation  of  potas- 
sium sulphocyanide. 

Ammonium  sulphocyanide  is  also  sometimes  used  in  photography 
as  a  fixing  agent. 

Mercury  sulphocyanide  was  for  some  time  used  in  the  preparation 
of  a  toy  known  as  Pharaoh's  serpent  and  invented  by  Barnett  in 
1866.  When  this  salt  is  mixed  with  potassium  nitrate  and  lighted, 
it  puffs  up  and  twists  and  winds  about,  making  it  appear  like  a 
serpent.  This  phenomenon  is  due  to  an  abundant  liberation  of 
nitrogen  and  vapors  of  carbon  bisulphide  and  mercury.  This  toy 
is  rather  dangerous,  as  mercury  sulphocyanide  is  a  very  poisonous 
compound.  Moreover,  the  same  results  may  be  obtained  by  oxidiz- 
ing with  nitric  acid  the  residue  of  the  purification  of  brown  coal- 
oils  (Vorbringer). 

Sulphocyanide  of  copper  is  much  used  in  the  preparation  of  sub- 
marine paints.  The  coat  applied  to  the  hulls  of  ships  prevents  by 
its  toxic  properties  the  crustaceans  from  adhering  to  the  vessel. 

Potassium  or  ammonium  sulphocyanide  is  frequently  used  in  the 
laboratories  in  testing  for  ferric  salts,  or  for  the  presence  of  nitrous 
compounds  in  nitric  acid. 

Among  the  other  cyanide  compounds  that  can  be  used  may 
also  be  mentioned  calcium  cyanate,  which  a  few  years  ago  was 
highly  praised  as  a  fertilizer  by  Camille  Faure,  and  hydrocyanic 
acid,  sometimes  used  in  medicine  in  pulmonary  diseases,  and  those 
in  which  inflammation  is  seriously  induced,  such  as  asthma,  whoop- 
ing-cough, etc. 


CONCLUSIONS. 


FROM  the  technical  and  economic  study  which  has  just  been 
made,  it  follows  that  the  cyanide  industry  has  been  improved  in  a 
remarkable  way,  especially  in  the  last  fifteen  years,  and  that  it  is 
now  in  a  most  interesting  period  of  progress. 

As  we  stated  at  the  beginning  of  this  work,  the  increase  in  the 
demand  has  been  the  chief  cause  of  these  improvements. 

At  the  present  time  the  old  processes,  i.e.,  those  based  on  the 
use  of  nitrogenous  organic  substances,  are  only  used  in  rare  cases. 
Cyanides  are  now  produced  almost  wholly: 

(1)  By  new  processes,  known  as  synthetic  processes. 

(2)  By  illuminating-gas  and  the  residues  produced  in  its  manu- 
facture. 

The  question  naturally  occurs  to  one,  Of  all  these  processes 
belonging  to  one  or  the  other  category,  which  is  or  which  are  the 
best?  This  question  is  very  hard  to  solve.  Nevertheless,  by 
relying  on  the  results  obtained,  it  may  be  possible  to  a  certain 
degree  to  answer  that  question  and  that  is  what  will  now  be 
attempted. 

The  synthetic  processes  have  the  great  advantage  of  producing 
potassium  cyanide  as  a  final  product.  But  in  most  of  these  processes 
this  advantage  is  counterbalanced  by  serious  objections:  the  tem- 
perature required  for  the  reaction  is  often  very  high,  from  which  it 
follows  Hi  at  losses  by  volatilization  occur,  besides  a  rapid  wear  and 
tear  of  the  apparatus.  Moreover,  the  conversion  is  very  often 
incomplete,  and  the  reactions  do  not  always  take  place  as  simply 
as  the  theory  would  lead  one  to  expect.  Notwithstanding  the 
numerous  efforts  of  investigators  and  manufacturers,  very  few  of 
these  processes  have  had  any  really  practical  application.  Not  one 

321 


322  CONCLUSIONS. 

of  the  synthetic  processes  using  nitrogen  and  alkali  metals  has  yet 
given  satisfactory  results.  At  one  time  great  hopes  were  placed 
on  the  processes  which  consisted  in  making  atmospheric  nitrogen 
act  on  metallic  carbides;  works  had  even  been  established  at  Frank- 
fort, but  the  results  never  came  up  to  expectations,  and  according 
to  information,  this  method  of  manufacture  is  now  abandoned,  or 
is  on  the  point  of  being  abandoned. 

On  the  other  hand,  the  methods  using  ammonia  appear  to  give 
satisfactory  results.  Among  those  which  still  use  the  oxids  or 
carbonates  of  the  alkalis,  two  only  deserve  to  be  kept  in  mind: 
those  of  Roca  and  of  the  Stassfurter  Chemische  Fabrik.  The  latter, 
however,  established  on  a  large  enough  scale,  seems  to  give  rather 
unsatisfactory  results. 

Only  the  methods  which  start  with  an  alkali  metal  (sodium), 
carbon,  and  ammonia,  with  the  intermediary  formation  of  cyanamide, 
seem  to  have  succeeded.  The  results  obtained  by  the  Deutsche  Gold 
und  Silber  Scheide  Anstalt  confirm  this  statement.  The  one  serious 
objection  is  the  relatively  high  cost  of  metallic  sodium  or  its  alloys. 

The  synthetic  processes  have  been  developed  especially  in  Ger- 
many and  England,  and  that  is  the  reason  that  the  cyanide  industry 
has  become  so  important  in  those  countries,  and  that  they  are  able 
to  deliver  these  products  much  cheaper  than  others. 

The  second  class  of  methods  for  the  production  of  cyanides, 
which  consists  in  the  extraction  of  cyanogen  compounds  from  the 
residues  of  the  manufacture  of  illuminating-ga  or  from  gas  itself, 
cannot,  properly  speaking,  be  considered  as  a  means  of  manufacture, 
as  it  is  but  an  adjunct  of  the  gas  industry,  on  which  it  depends 
absolutely.  Nevertheless,  if  gas  manufacturers  could  see  what 
benefits  there  are  to  be  derived  from  it,  it  would  constitute  a  profit- 
able and  important  source  of  the  cyanide  production,  and  probably 
might  provide  for  a  great  portion  of  the  demand.  This  class  of 
processes  may  therefore  be  of  great  service,  especially  if  one  con- 
siders that  these  compounds  form  themselves,  and  that  without 
injuring  the  quality  of  the  gas  produced,  the  manufacturer  may 
still  increase  the  amount  of  cyanogen  compounds;  and,  finally,  that 
their  recovery  is  made  with  very  little  expense. 

The  processes  which  extract  the  cyanogen  from  the  gas  directly 
are  those  which  appear  to  give  the  best  results,  economically  as 


CONCLUSIONS. 


32S 


well  as  from  the  standpoint  of  yield,  and  among  these  the  processes 
of  Julius  Bueb  seem  to  have  an  important  future  industrially  on 
account  of  their  simplicity  and  the  very  satisfactory  results  which 
they  furnish. 

It  is  true  that  the  gas  industry  yields  only  ferrocyanides  which 
it  is  then  necessary  to  convert  into  sodium  or  potassium  cyanide. 

As  we  have  seen,  this  conversion  is  done  very  simply  by  the 
Rossler-Hasslacher  Co.'s  process;  that  is,  by  means  of  metallic 
sodium.  This  process  is  practically  the  only  one  now  in  use,  and 
it  gives  excellent  results.  When  the  price  of  sodium  does  not  exceed 
250  francs  per  100  kg.,  this  process  is  profitably  conducted,  otherwise 
not.  This  same  statement  also  applies  to  synthetic  processes  using 
this  metal. 

Another  class  of  processes  very  similar  to  those  based  on  the 
manufacture  of  gas  is  that  which  consists  in  converting  the  nitrogen 
of  the  sugar-beet  vinasses  into  cyanides.  As  is  well  known,  the 
sugar  industry  has  grown  enormously  in  Germany  and  France, 
and  it  has  been  seen  that  the  dry  distillation  of  vinasses  may 
profitably  produce  cyanides.  Here  again,  the  discoveries  of  Bueb 
of  Dessau  seem  to  give  the  best  results;  therefore  it  is  to  be  hoped 
that  soon  all  the  manufacturers,  distillers,  or  gas-makers  will  know 
in  France,  as  well  as  in  England  and  Germany,  how  to  derive  all 
the  "cyanogen  which  their  industries  are  capable  of  producing,  and 
that  under  the  simplest  and  most  profitable  economic  conditions. 

DENSITY  OF  SOME  CYANOGEN  COMPOUNDS. 


Name. 

Density. 

Weight  per  Liter. 

Cyanogen     

1   8064 

2  335  (0°  at  and  760  mm  ) 

'  '         liquid 

/  0.866  at  17°.  2 

Hydrocyanic  acid  (anhydrous 
liquid)            .        

I  0  .  706  at  7° 
JO.  7058  at  7° 
\  0  6969  at  18° 

Hydrocyanic  acid,  g£is           .  . 

0  947 

1  210  (at  0°  and  760  mm  ) 

Ammonium  sulphocyanide.  .  . 

Potassium  cyanide  
ferricyanide  
ferrocyanide     .... 

1.31 
(1.3075  at  13°  Clarke) 
1.52 
1.83 
1.91 

sulphocyanide.     .  . 
Sodium  nitroprussiate,  crys- 
tallized      

1.89 
1.71 

• 

.324 


CONCLUSIONS. 


TENSION  OF  CONVERSION  OF  CYANOGEN. 

(L.  TROOST  AND  HAUTEFEUILLE.) 
Temperature.  Tension  of  Conversion. 

502 54  mm. 

559 123  " 

575 129  " 

587 . 157  " 

599 275  " 

601 318  " 

620 868  " 

640 1310  " 

HEAT  OF  FORMATION  OF  CYANIDES. 

Heat  Liberated,  the  Compound  being 
Name.  Components. 

Gas.  Liquid.          Solid.       Dissolved. 

Potassium  cyanide CN  +  K  +  67 . 6  64 . 7 

.Sodium  "      CN  +  Na  +60.4  +59.9 

Calcium  "      CN  +  Ca  +57.7 

Barium  "      CN  +  Ba  z-4.3  z-3.4 

Zinc  "      CN  +  Zn  +29.3 

Mercury  "      CN  +  Hg           —             —          +11.9  +17.9 

.Silver  "      CN  +  Ag  +  3.6 

HEAT  OF  VOLATILIZATION  (FROM  LIQUID  STATE). 

ON  BASIS  OF  ONE  VOLUME   OF  VAPOR   (22'.22)  =  1   MOL.   IN  GRAMS. 

Hydrocyanic  acid CNH  —5.7 

Cyanogen  chloride .CNC1  -8.3 

HEAT  OF  SOLUTION  IN  WATER  IN  GASEOUS  STATE. 
1  MOL.=22'.22(l  +  otf)  AT  760  MM. 

Hydrocyanic  acid +6.1 

Cyanogen +6.8 

CRITICAL  TEMPERATURE  OF  CYANOGEN  (DEWAR) 
Critical  tern.  Atmospheric  pressure. 

124°. 0.  .:.-,  .  61  7 


CONCLUSIONS. 


325 


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00  10  <N  Oi 

1  Igj^^i^  1  1  1  1  1  1  1  1  !  1  1  1  1  1  1  i     II 
i  +  i  + 


CO  tO  IQ  00  I>  CO 

'^^\  I  II 1 1 1 1 1 1 1 1 1 1 1  I  II 

I  I  +  I  + 


IO  IO  i-H  i-l  1-H 

CO<Ml>I>i-ITH^^iOtOO5COCOi-irHOi 
<M  tO  (N  (N  CO  CO  •*  Tt^  CO  O  Tji  <M  (N  QO  00  »O 


(N  (N 

OOQO        T}H'T}H 
O  O        OO  OO 


!z^«mc5jwM^iassBa44W 


W    S    df   M 


o 
+ 


Hl| 

tf 


oooo' 


° 
^ 


s 

^     -2 
^         ^ 

I    1 
s   £ 


'£ 

^s 

^  g 


s 

° 


326 


CONCLUSIONS. 


T-ITH  l>O5rt<  T* 


l>  CO 

COr-H 


t>  Oi  t>i-H 


•AV  4^^  »^,   I    i    I   T-H   I   O^  Oi  ^H  t>«- 

^^H«0  eq     CC^HOOt- 

i-H  l-H      I   '   I      ' 


I     + 


O*  CO       CO  CO  .T}* 

&R is 

^H  CO    '    i-( 


1 1  r- 


CD  O  CO  rt<  O5  O   00   O  CO  1C  00  (N  O   rfi  CO  (M  »O 
CO  CO  CO  CO  iO  ' 


<N    il^    iCCCOcCcDiCcO    il>t^T-iO 

1>      |     00      ICOT^T-IOCCIO      |lCr-*rHC^ 


++++++ 


1 1 1 1 1 1 1 


1 1 1 1 


I  i  ! 


OiOOcO 

^^^'    I     I     I     I     I 

I    +    I       ' 


£ 

+  02  rr>  &  &  &  &  ^>> 

^o-M55^5t§S£^?  +  ^  +  +  +  +00  ^ 

0  +  +  +  +  +  +  + +,+  +  +  +  + 


asal      £      P 

-- 


i^miillli  jinliiijilr ' 


CONCLUSIONS. 


327 


1 

.s5 


o 


.a- 


1 


1i   !i 


02      <- 

Q    fc 


I   2 


j3 

^OJ  S 

,O  ^        >> 

3  -  T! 


^ 

W) 


S  rf  I 


l.s  l«.a 

H      *^  ^^  «rH 


,-g  ^          fl 

cr 


-2-^      ^ 


:-8 
;  & 
'-« 


•  o, 


!llli.LJI 


! 


^    rj    3    (w    O) 
B    B*S    O   O 


.2     ^ 
^     'Scs 

s    si 


328 


CONCLUSIONS. 


Fe 


•« 


g, 


-3 


III! 

n 


s       .|      |  .-.iji 


II 


11 


rdy  precipi 
excess 


tB 


•a  § 

•§.§s 


l-S-9^ 

5    S-e'® 


l 


CONCLUSIONS. 


329 


DEGREE  BAUME. 

WHICH    BOILING    SALT    SOLUTION    SHOULD    INDICATE    SO    AS    TO    PRODUCE    BEAUTIFUL 

CRYSTALS    ON    COOLING. 

Mercury  cyanide 20°  B. 

Potassium  ferrocyanide 38? " 

Ammonium  sulphocyanide 18°    " 

COOLING  MIXTURE. 
A  mixture  of 

Ammonium  sulphocyanate 133 

Water 100 

produces  a  lowering  in  temperature  of — 31°  (Ruddorf). 

FORMATION  OF  DISSOLVED  SALTS,  DISSOLVED  ACID,  DILUTE  BASE. 

4KOH +54.0  cal. 

,,  n    „  2BaO. +56.0    " 

FeCy6H4  dissolved^     ^^ ;    +4g  g    „ 

|Fe203ppt +25.2    " 

Fe2Cyi2H6dissolved  +6KOH +58.0    " 

fKOH.  .../. +14.0    " 

CySHdissolved       +  (  ^ +12  5    M 

HEAT  OF  COMBUSTION. 

C2  +  N2 , 262.5  cal. 

C  +  N  +  H 158.0  cal.  (gas) 

DENSITY  OF  SOLUTIONS. 

POTASSIUM   FERRICYANIDE. 


Density. 


.0261 
.0538 
.0831 
.1139 
.1462 
.1802 


Per  Cent.  Potassium 
Ferricyanide. 


5 
10 

15 
20 
25 
30 


POTASSIUM    SULPHOCYANIDE. 


Density. 


.020 
.026 
.031 
.034 
.042 
.050 
.070 
.077 
.137 


Per  Cent.  Potassium 
Sulphocyanide. 

7.0' 
10 

11.1 
12.5 
14.2 
16.6 
20 
25 
33.3 


330 


CONCLUSIONS. 


DENSITY  OF  SOLUTIONS. 

HYDROCYANIC    ACID. 


Density. 

Per  Cent.  CNH. 

0.9988 

1 

0.9974 

2 

0.9958 

3 

0.9940 

4 

0.9919 

5 

0.9895 

6 

0.9869 

7 

0.9840 

8 

0.9811 

9 

0.9781 

10 

0.9716 

12 

0.9570 

16 

POTASSIUM    FERROCYANIDE. 


Density. 

Per  Cent.  Potassium 
Ferrocyanide. 

.0116 

2 

.0234 

4 

.0356 

6 

.0479 

8 

.0605 

10 

1.0734 

12 

.0866 

14 

.0999 

16 

1.1136 

18 

1.1215 

20 

AMMONIUM   SULPHOCYANIDE. 


Density  at  15°. 

Per  Cent.  CNS  .  NH* 

.020 

10.0 

.026 

11.1 

.031 

12.5 

.034 

14.2 

.042 

16.6 

.050 

20.0 

.070 

25.0 

1.077 

33.0 

1.137 

50.0 

APPENDIX. 


DIGEST  OF  UNITED  STATES  PATENTS  RELATING  TO 
CYANIDE  PROCESSES  FOR  THE  RECOVERY  OF  PRE- 
CIOUS METALS  .* 

THIS  digest  covers  most  of  the  patents  included  in  the  following  classes  and 
subclasses  of  the  United  States  Patent  Office  classification: 

Class  75. — Metallurgy. 

Subclass  18. — Solutions  and  Precipitation.  » 

Subclass  86. — Solutions  and  Precipitation — Apparatus. 
Subclass  185. — Cyanides. 

Class  204.— Electrolysis. 

Subclass  15. — Aqueous  Bath,  Ores. 

Some  of  the  patents  in  these  categories  are  quite  foreign  to  the  subject  under 
consideration,  and  many  but  indirectly  related  to  it.  It  has  been  thought,  how- 
ever, from  the  form  which  discussions  of  patent  issues  often  take,  to  include  the, 
latter.  The  aim  in  making  the  digest  has  been  to  give  such  a  sketch  as  will  indi- 
cate the  nature  of  the  invention  and  what  is  claimed  by  the  inventor,  this  gen- 
erally being  done  by  an  acttial  abstract  from  or  paraphrase  of  the  words  of  the 
letters  patent,  but  no  responsibility  is  assumed  for  the  opinions,  theories,  or  claims 
thus  set  forth.  Other  related  patents  may  have  been  granted  which  do  not  appear 
in  this  digest,  because  they  are  not  embraced  in  the  subclasses  enumerated.  Thus, 
the  patents  number  229586,  to  Thomas  C.  Clark;  236424,  to  H.  W.  Faucett;  and 
244080,  to  John  F.  Sanders,  do  not  appear  in  this  digest,  because  the  first  two  are 
classified  under  subclass  "  Reducing  and  Separating — Disintegrating  Ores,"  and 
the  third  under  subclass  "  Reducing  and  Separating — Gold  and  Silver J1  and  neither 
of  these  subclasses  is  included  in  this  digest. 

CLASS  75.— METALLURGY. 
SUBCLASS  18. — SOLUTIONS  AND  PRECIPITATION. 

1551,2 — August  12,  1856.  W.  ZIERVOGEL.  Improvement  in  processes  of  separa- 
ting silver  from  the  ore. — The  application  of  water  or  a  solution  of  sulphate  of  cop- 
per slightly  impregnated  with  sulphuric  acid  instead  of  lead,  quicksilver,  or  salt, 
hitherto  used  for  this  purpose,  to  the  process  of  separating  silver  from  copper 
and  other  ores,  rendering  thereby  this  separation  easier,  shorter,  less  expensive, 
and  not  noxious  to  the  health  of  the  operator. 

*  Reprinted  from  "  Precious  Metals  Recovered  by  Cyanide  Processes  "  by  Charles  E.  Munroe, 
Ch.  D  with  the  kind  permission  of  the  Department  of  Commerce  and  Labor. 

331 


332  APPENDIX. 

19991 — April  20,  1858.  I.  GATTMAN.  Improvement  in  the  treatment  of  sul- 
phureted  ores. — The  use  of  sulphuric  acid  in  connection  with  the  hydrate,  car- 
bonate, or  sulphate  of  potash  or  soda,  or  with  any  compound  thereof,  in  the  mode 
of  working  the  native  metallic  sulphurets. 

3584.2 — July  8,  1862.  J.  SHAW.  Improved  apparatus  for  saving  silver  from 
waste  solutions. — Attaching  to  the  waste  pipe  of  the  sink  or  basin  into  which  per- 
sons using  silver  in  solutions  suffer  them  to  be  wasted,  a  vessel  so  arranged  and 
constructed  that  the  liquids  passing  from  the  sink  shall  run  into,  through,  and 
out  of  said  vessel,  and  between  the  time  of  entering  said  vessel  and  escaping  there- 
from shall  be  brought  into  contact  with  such  chemicals  or  metals  as  will  cause 
the  whole  or  any  part  of  the  silver  contained  in  solution  to  be  precipitated  and 
retained  in  said  vessel,  while  the  worthless  material  is  allowed  to  escape.  (This 
patent  was  reissued  as  follows:  Reissue  1651,  April  5,  1864;  reissue  3506,  June  15, 
1869;  reissue  4030,  June  14,  1870;  reissue  4969,  Division  A,  July  9,  1872;  and 
reissue  4970,  Division  B,  July  9,  1872.) 

46875 — March  21,  1865.  W.  BRUCKNER.  Improved  process  for  refining  amal- 
gam.— The  application  and  use  of  bichloride  of  copper,  or  its  equivalent,  together 
with  iron  pyrites  and  salt,  without  reference  to  the  exact  proportions  of  each 
ingredient. 

46983 — March  28,  1865.  G.  W.  BAKER.  Improvement  in  treating  ores. — In 
order  to  produce  a  valuable  metal  or  metals  now  almost  wholly  cast  away  in  the 
treatment  of  auriferous  and  argentiferous  pyrites,  the  inventor  proposes  to  take 
the  calcined  ores  as  they  come  from  the  furnaces,  and,  having  them  weU  pul- 
verized, subject  them  to  the  action  of  sulphurous  acid  in  tanks  located  over  the 
main  discharge  flues  of  his  furnaces,  whereby  a  sufficient  heat  may  be  obtained 
to  assist  in  the  reaction  of  the  acid  before  mentioned.  The  sulphurous  acid  thus 
used  is  to  be  formed  and  collected  by  compelling  the  sulphurous  vapors  discharged 
from  the  roasting  furnace  to  pass  over,  through,  and  in  contact  with  water,  so 
that  sulphurous  acid  will  be  formed  and  collected  in  a  properly  arranged  tank 
or  tanks,  from  whence  it  may  be  conveyed  to  the  ore  tanks,  and  there  mixed  with 
the  ore  thoroughly  by  agitation  in  any  manner  most  convenient.  After  the  ore 
has  been  subjected  to  the  action  of  the  acid  for  a  couple  of  hours  the  oxide  of  cop- 
per will  be  replaced  by  a  sulphate  soluble  in  water,  and  the  oxide  of  iron  will  be 
partially  brought  into  the  same  condition  Should  there  be  any  gold  or  silver 
held  in  solution  these  metals  will  be  reduced  to  the  metallic  state.  The  solution 
is  then  drawn  off  by  siphon  or  otherwise  and  conveyed  to  another  tank  or  vat 
for  subsequent  treatment,  either  by  cementation  or  precipitation  for  the  copper 
and  evaporation  for  the  sulphate  of  iron.  The  ore  thus  treated  may  then  be 
lixiviated  by  water  to  wash  out  all  the  acid,  and  this  water,  which  will  still  hold 
some  dilute  solution  of  the  baser  metals,  may  be  conveyed  to  the  acid  tank  and 
used  for  the  further  formation  of  sulphurous  acid.  By  this  means  the  most  con- 
centrated solution  is  alone  permitted  to  pass  to  the  tank  or  vat  for  further  treat- 
ment. It  may  be  considered  a  well-settled  fact  that  in  all  processes  of  calcina- 
tion some  portion  of  the  precious  metals,  if  such  ores  are  under  treatment,  escape 
mechanically  or  in  a  vaporized  form.  This  loss,  great  or  small,  as  the  case  may 
be,  has  heretofore  been  to  a  great  degree  irreclaimable.  It  is  claimed  as  a  part 
of  this  improvement  that  such  loss,  whether  mechanical  or  in  the  form  of  vapor, 
is  wholly  prevented  by  arresting  their  escape  and  returning  them,  either  in  solu- 
tion or  in  the  sediment  of  the  liquid  acid,  to  the  ore  when  treated  in  the  ore  tanks. 


? — April  18,  1865.  W.  L.  FABER.  Improved  process  of  working  silver 
ores. — The  invention  consists  in  a  process  which  is  divided  in  eight  different  manipu- 
lations, viz.,  smelting  the  ore,  pulverizing,  roasting  at  low  heat,  extracting  sul- 
phates with  water,  roasting  residue  with  salt,  melting  with  soda,  precipitating 
silver,  precipitating  copper. 

49637 — August  29,  1865.  S.  F.  MACKIE.  Improved  process  for  treating  ores. — 
The  mode  of  obtaining  a  rich  gold  residue  from  ores  of  gold  by  treating  the  ores 
by  roasting  and  fusing,  and  subjecting  the  roast  to  the  action  of  acids. 

52834 — February  27,  1866.  J.  H.  ELWARD  and  J.  L.  HAYES.  Improved  process 
for  separating  gold  and  silver  from  ores. — The  process  of  oxidizing  sulphurets  con- 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  333, 

taining  the  precious  metals  and  converting  them  into  sulphates  by  the  use  of  solu-. 
tions  of  nitrates. 

56765 — July  SI,  1866.  E.  LAMM.  Improved  method  of  preparing  gold  for 
dentists. — The  use  of  saccharine  substances  to  precipitate  gold  from  its  solutions, 
thereby  forming  a  mass  of  crystal  shreds  extremely  useful  and  convenient  for 
dental  and  other  purposes. 

148356 — March  10,  1874-  J.  DOUGLAS,  Jr.  Improvement  in  extracting  silver 
from  its  ores. — The  process  of  utilizing  the  waste  liquors  of  the  ordinary  ore-chlori- 
dizing  process,  by  allowing  the  insoluble  matters  contained  in  said  liquors  to  pre- 
cipitate, and  then  evaporating  the  clear  supernatant  liquid  to  obtain  the  soluble 
chlorides,  which  are  reapplied  in  treating  fresh  ores. 

207695 — September  3,  1878.  J.  TUNBRIDGE.  Improvement  in  separating  metals 
from  waste  solutions. — The  process  of  separating  precious  metals  from  watery 
solutions,  in  which  said  metals  are  suspended  by  passing  the  watery  solutions 
or  puds  through  a  bath  of  oil  or  hydrocarbon  liquid. 

219961 — September  23,  1879.  F.  M.  LYTE.  Improvement  in  extracting  metals 
from  ores. — In  the  treatment  of  ores  containing  lead,  zinc,  silver,  and  copper,  the 
method  of  securing  the  neutralization  of  the  solutions  of  soluble  bases,  economizing 
acid,  and  carrying  over  the  least  possible  quantity  of  silver  and  lead,  which  con- 
sists in  treating  the  raw  ores  with  an  acid  solution  partially  saturated  by  previous 
attack  on  the  ores,  and  treating  the  partially  exhausted  ore  by  raw  acid  before 
the  latter  is  admitted  to  the  raw  ore,  the  said  steps  being  conducted  in  a  continu- 
ous, alternate,  and  methodical  manner. 

227963— May  25,  1880.     W.  M.  DAVIS.     Depositing  gold  from  its  solutions. — The 
process  of  obtaining  gold  from  its  solution  by  bringing  said  solution  in  contact 
\/'       with  carbon,  and  thereby  depositing  the  gold  upon  it,  and  of  subsequently  obtain- 
ing the  gold  from  the  carbon  by  calcination  or  other  equivalent  means. 

287737 — October  30,  1883.  C.  A.  STETEFELDT.  Process  of  treating  sulphides. — > 
The  process  of  treating  sulphides,  such  as  those  obtained  from  the  lixiviation  process 
of  silver  ores,  said  process  consisting  in  first  exposing  said  sulphides  to  the  action 
of  dilute  sulphuric  acid  in  the  presence  of  nitrate  of  soda,  then  converting  the 
nitric  oxide  which  escapes  into  nitrous  acid  and  nitric  acid,  and  finally  carrying 
on  the  process  by  means  of  a  mixture  of  nitrous  acid  and  nitric  acid  with  dilute 
sulphuric  acid. 

288838 — November  20,  1883.     J.  MILLER.     Process  of  recovering  metallic  particles 

from  water. — The  method  of  recovering  metals  in  suspension  in  liquid,  consisting, 

\          essentially,  in  forcing  such  liquid  through  a  filtering  medium  having  a  capacity 

^"     of  expansion,  and  resisted  by  a  rigid  inclosing  vessel  or  medium,  and  then  burning 

the  filling  material  or  otherwise  separating  the  metal  therefrom. 

290258 — December  18,  1883.  J.  MILLER.  Apparatus  for  collecting  and  saving 
metallic  particles. — An  apparatus  for  recovering  metals  or  metallic  compounds  in 
X/"  liquids,  consisting  of  a  rigid  tank,  perforated  on  one  side,  in  combination  with 
an  entrance  pipe,  provided  with  a  trap  and  a  pressure  device. 

290458 — December  18,  1883.  J.  MILLER.  Method  of  recovering  metals. — The 
improved  method  for  recovering  metallic  particles,  slimes,  and  similar  material 
containing  metal  from  liquids,  consisting,  essentially,  in  conducting  the  liquid 
and  metal-bearing  material  to  a  settling  tank,  allowing  the  gangue  to  fall  to  the 
bottom,  drawing  off  the  liquid,  and  forcing  it  under  hydrostatic  pressure  through 
a  filter  press,  and  removing  and  drying  the  filtrate. 

292605 — January  29,  1884.  C-  P.  WILLIAMS.  Art  of  extracting  gold  by  means 
of  alkaline  sulphides. — In  the  art  of  extracting  gold  from  ores  and  artificial  gold- 
\f  bearing  products  by  means  of  alkaline  sulphides,  the  process,  which  consists  in 
mixing  the  gold-bearing  material  with  carbon  and  an  alkaline  sulphate  (or  the 
equivalents  of  sucii  carbon  and  alkaline  sulphate),  calcining  said  mixture  in  a 
non-oxidizing  atmosphere  at  a  temperature  below  the  point  of  fusion  of  the  charge, 
cooling  the  mass  out  of  contact  with  the  air,  and  leaching  the  cooled  mass  with 
water  to  dissolve  out  the  soluble  sulphides,  and  recovering  the  gold  therefrom  by- 
precipitation. 


334  APPENDIX. 

877809 — February  14,  1888.  T.  KIDDIE.  Process  of  separating  precious  metals 
and  impurities  from  solutions  of  copper,  salts,  ores,  mattes,  etc.,  in  acids. — The  process 
of  removing  precious  metals  and  impurities  from  copper  mattes,  ores,  bullion, 
etc.,  consisting  in  dissolving  the  same  after  desulphurization  and  calcination  in 
sulphuric  acid,  in  quantities  sufficient  to  form  a  neutral  solution,  and  in  adding 
iron  hydrates  to  the  neutral  solution,  whereby  the  impurities  are  precipitated 
and  settle  with  the  precious  metals  not  dissolved  by  the  sulphuric  acid,  leaving 
a  comparatively  pure  solution  of  iron  and  copper  salts. 

881809 — April  84,  1888.  R.  OXLAND  and  C.  OXLAND.  Treatment  of  ores  and 
materials  containing  sulphur  for  the  extraction  of  metals  and  other  constituents, — The 
method  of  treating  raw  or  unburned  sulphuret  ores  of  copper  and  iron  to  render 
the  copper  soluble  in  water,  while  leaving  the  iron  for  the  most  part  insoluble  and 
rendering  the  sulphur  in  the  ore  available  for  the  manufacture  of  sulphuric  acid, 
consisting  in  mixing  the  finely  pulverized  ore  to  a  semifluid  consistency  with  sul- 
phuric acid  and  solution  of  persulphate  of  iron,  heating  the  mixture  to  a  tem- 
perature such  as  to  evolve  sulphurous-acid  vapor,  and  collecting  and  condensing 
isuch  acid  vapor. 

887688 — August  14,  1888.     A.  H.  Low.     Extraction  of  zinc  from  ores. — The 

Srocess  of  extracting  zinc  from  ores  containing  precious  metals,  consisting  in  leach- 
g  the  ore  with  an  aqueous  solution  of  sulphurous-acid  gas  to  dissolve  out  the 
zinc,  and  then  boiling  the  leached  liquor  to  expel  the  sulphurous-acid  gas  and 
cause  a  precipitation  of  the  zinc. 

403615 — May  21,  1889. — E.  H.  RUSSELL.  Process  of  leaching  ores  with  hypo- 
sulphite solutions. — The  process  of  extracting  metal  from  ores  and  metallurgical 
products,  which  consists  in  introducing  into  the  ore  or  product  carbonate  of  soda, 
then  treating  the  mass  with  a  solution  of  sulphate  of  copper,  and  then  treating 
it  with  a  hyposulphite  solution. 

413808 — October  29,  1889.  J.  S.  MACARTHUR.  Process  of  leaching  ores. — The 
process  of  treating  ores  containing  oxides  or  carbonates  of  earth  metals,  consist- 
ing in  first  subjecting  such  ores  to  the  action  of  a  proportionate  quantity  of  a  solu- 
tion of  a  ferrous  salt  or  a  bisulphate  of  an  alkali  to  combine  with  the  oxides  or  car- 
bonates of  earth  metals,  and  then  treating  the  ores  with  an  acid  or  salt  to  obtain 
the  contained  metals. 


[ — February  11,  1890.  R.  PEARCE.  Process  of  extracting  silver  from 
copper  ores,  mattes,  and  other  copper  products. — The  process  of  separating  silver 
from  ores  or  mattes  containing  base  metals,  which  consists  in  mixing  with  the 
finely  pulverized  ore  or  mattes  a  quantity  of  sulphate  of  sodium  or  potassium 
/  equal  to  2  per  cent.,  then  roasting  the  mixture,  and  finally  leaching  out  by  hot 
water  to  obtain  the  sulphate  of  silver. 

440143 — November  11,  1890.  E.  DODE.  Process  of  separating  gold  and  plati- 
num from  other  metals  in  solution. — The  process  of  separating  from  an  acid  solu- 
tion of  gold,  platinum,  copper,  and  tin  the  metallic  constituents  of  said  solution, 
which  process  consists  in  first  subjecting  the  entire  solution  in  the  presence  of 
ether  to  agitation  until  the  ether  becomes  yellow,  in  then  decanting  the  remaining 
solution  from  the  yellow  ether,  in  then  subjecting  said  remaining  solution  to  agita- 
tion in  the  presence  of  essence  of  lavender  until  the  essential  oil  becomes  brown, 
..  and  in  then  decanting  from  the  brown  essential  oil  the  remaining  solution  and 
e  adding  thereto  ammonia. 

442016 — December  2,  1890.  C.  L.  COFFIN.  Process  of  treating  ore  containing 
lead,  silver,  and  zinc. — The  process  of  treating  ore  containing  lead,  silver,  and 
zinc  to  remove  the  zinc  preparatory  to  smelting,  consisting  in  first  roasting  the 
ore,  then  leaching  the  ore,  filtering  the  leach  fluid  through  carbon,  then  subject- 
ing the  leach  fluid  successively  to  the  action  of  metallic  lead  and  of  metallic  zinc, 
and  finally  precipitating  the  zinc  held  in  solution  in  the  leaching  fluid. 

444997 — January  20,  1891.  W.  WEST.  Process  of  treating  zinc  ores. — The 
process  of  eliminating  zinc  from  complex  ores,  which  consists  in  roasting  the  ore 
to  form  sulphurous-acid  gas  and  oxidize  the  zinc,  then  cooling  this  gas  to  a  tem- 
perature of  180°  F.  or  below,  and  passing  the  same  in  gaseous  form  in  conjunction 
with  steam  and  without  oxidation  into  sulphuric  acid  through  a  previously  roasted 


OF  THE 

UNIVERSITY 

PATENTS  RELATING  TO  CYAN^T  335 


charge  to  form  soluble  sulphite  of  zinc,  and  then  immediately  leaching  out  and 
separating  the  zinc  sulphite  with  water  at  a  temperature  below  180°  F. 

449814  —  April  7,  1891.  S.  W.  CRAGG.  Lixiviation  process  of  and  apparatus 
for  the  extraction  of  gold  or  silver.  —  The  process  of  restoring  the  oxygen  in  a  hypo- 
sulphite solution  in  the  lixiviation  process,  which  consists  in  passing  a  current  of 
air  through  the  ore  pulp  while  the  said  solution  is  in  contact  therewith,  and  a 
leaching  vat,  a  grating  at  the  top  thereof  through  which  ore  pulp  and  water  are 
introduced  to  the  interior  of  the  vat,  and  a  system  of  crossed  separated  bars  within 
the  vat  through  which  the  ore  pulp  and  water  pass,  combined  with  an  endless- 
apron  filter  on  which  the  ore  pulp  and  water  fall  from  the  said  crossed  bars,  a,trough 
beneath  the  filter  to  receive  the  water,  and  a  lixiviation  vat  into  which  the  apron 
filter  discharges  the  ore  pulp. 

471616—  March  29,  '1892.  J.  LEEDE.  Process  of  treating  refractory  ores.  —  The 
continuous  process  of  treating  refractory  auriferous  and  argentiferous  ores,  which 
consists  in  subjecting  the  ore  to  the  continuous  action  of  an  oxidizing  blowpipe 
flame  in  direct  contact  with  the  ore  at  a  moderate  heat,  intermittently  subjecting 
the  heated  ore  to  the  action  of  .water,  agitating  the  ore,  and  then  repeating  the 
operation  at  a  higher  heat,  and  finally  subjecting  it  to  an  oxidizing  roast  without 
chills,  whereby  the  volatile  elements  are  driven  off,  the  oxidizable  elements  or 
compounds  are  oxidized,  and  the  precious  metals  are  left  free  and  in  suitable  con- 
dition for  amalgamation  or  chlorination. 

473186  —  April  19,  1892.  P.  C.  CHOATE.  Method  of  producing  metallic  zinc.  — 
The  process  of  producing  metallic  zinc  from  its  ores,  which  consists  in  separating 
the  zinc  and  the  equally  volatile  and  more  volatile  constituents  from  the  less  vola- 
tile constituents  of  the  ore  by  the  use  of  heat  and  a  reducing  agent,  then  volatiliz- 
ing and  oxidizing  the  reduced  metal,  thereby  obtaining  a  condensed  oxidized 
fume,  subjecting  this  fume  to  a  moderate  heat  in  order  to  expel  its  soluble  con- 
stituents more  volatile  than  zinc,  treating  the  remaining  product  with  dilute  sul- 
phuric acid  as  a  solvent,  and  finally  subjecting  the  resulting  solution  to  the  action 
of  an  electric  current  to  precipitate  the  zinc. 

481499  —  August  28,  1892.  G.  T.  LEWIS  and  C.  V.  PETRAEUS.  Process  of 
treating  sulphide  ores  of  zinc  and  lead.  —  The  process  of  recovering  lead  and  zinc 
from  sulphureted  lead  and  zinc-lead  ore,  which  consists  in  roasting  the  ore,  then 
smelting  the  roasted  mass*  and  exposing  the  fumes  or  volatile  matter  produced 
by  said  smelting  to  the  action  of  the  gases  which  are  volatilized  in  the  roasting 
of  said  ore,  together  with  water,  and  then  separating  the  zinc  solution  from  the 
insoluble  lead  compound  and  recovering  the  zinc  and  lead. 

483924  —  October  4,  1892.  T.  S.  HUNT  and  J.  DOUGLAS.  Process  of  separating 
copper  from  cupriferous  nickel  ores.  —  The  method  of  separating  the  copper  from  a 
solution  containing  copper  oxide  and  oxides  of  iron  and  nickel  to  produce  nickel- 
iferous  iron,  which  consists  in  first  adding  common  salt  to  the  said  solution,  then 
passing  a  stream  of  sulphurous-acid  gas  through  the  said  solution,  then  precipi- 
tating the  last  traces  of  the  copper  in  the  form  of  metallic  copper,  and  subsequently 
crystallizing  out  the  nickel  and  iron  and  calcining  and  smelting  the  product  to 
obtain  nickeliferous  iron. 

483972  —  October  4,  1892.  C.  WHITEHEAD.  Process  of  treating  mixtures  con- 
taining sulphides  of  precious  metals  and  copper.  —  The  process  of  treating  a  mix- 
ture containing  sulphides  of  the  precious  metals  and  of  copper,  which  consists 
in  mixing  the  sulphides  with  solution  of  a  salt  of  silver,  whereby  a  soluble  salt 
of  copper  is  formed  and  sulphide  of  silver  is  precipitated,  separating  the  solution 
containing  the  copper  from  the  residue  containing  the  precious  metals,  roasting 
this  residue  to  reduce  the  precious  metals  to  the  metallic  state,  treating  the 
reduced  metals  with  hot  sulphuric  acid  to  dissolve  the  silver,  separating  the  silver 
solution  from  the  residue,  and  melting  the  final  residue. 

490068  —  January  17,  1893.  F.  P.  DEWEY.  Process  of  treating  mixtures  con- 
taining sulphides:  —  The  process  of  treating  mixtures  containing  sulphides  of  silver 
and  copper,  which  consists  in  heating  the  sulphides  with  strong  sulphuric  acid 
to  convert  the  sulphides  into  sulphates  and  dissolve  the  sulphate  of  silver,  adding 
water,  to  bring  the  sulphate  of  copper  also  into  solution,  drawing  off  the  resultant 


336  APPENDIX. 

solution,  precipitating  the  silver  therefrom  by  metallic  copper,  and  recovering 
the  sulphate  of  copper  from  the  remaining  solution. 

490193 — January  17,  1893.  A.  FRENCH.  Process  of  obtaining  gold,  silver, 
and  copper  from  ores. — In  processes  for  obtaining  gold,  silver,  and  copper  from 
ores,  the  treatment  of  the  ores  by  pulverizing,  mixing  therewith  small  percentages 
of  niter  cake  or  bisulphate  of  soda  and  common  salt,  furnacing  at  a  red  heat,  and 
then  leaching. 

497473— May  16,  1893.  W.  R.  INGALLS  and  F.  WYATT.  Process  of  treating 
complex  or  sulphide  ores. — The  process  of  treating  complex  sulphide  ores,  which 
consists,  first,  in  subjecting  the  ore  to  a  sulphatizing  roasting;  second,  lixiviating 
the  roasted  ore  with  water  and  sulphuric  acid  and  removing  the  iron  therefrom 
if  necessary;  third,  precipitating  the  zinc  from  said  solution  in  the  form  of  car- 
bonate or  carbonate  and  hydroxide  by  the  use  of  sodium  carbonate  and  subse- 
quently converting  the  same  into  zinc  oxide;  fourth,  evaporating  the  sodium 
sulphate  obtained  from  the  zinc  sulphate  solution  and  heating  the  same  with  sodium 
chloride  and  coal  to  convert  it  into  sodium  sulphide;  fifth,  converting  the  sodium 
sulphide  into  bicarbonate  of  soda  by  dissolving  the  same  in  water  and  treating  the 
solution  with  carbonic  acid  gas;  and  lastly,  converting  the  bicarbonate  of  soda 
into  sodium  carbonate  by  heating  the  same  to  drive  off  the  hydrogen  and  car- 
bonic acid  gas. 

609058— November  21,  1893.  E.  WALLER  and  C.  A.  SNIFFIN.  Method  of 
concentrating  ores. — The  method  of  concentrating  argentiferous  lead  carbonate 
ores,  which  consists  in  dissolving  out  lead  from  the  ore  with  the  aid  of  acetic  acid 
real  or  combined,  and  water,  out  of  contact  with  the  air  whereby  the  lead  and 
carbonic  acid  eliminated  from  the  ore  are  rendered  capable  of  utilization  in  the 
arts,  and  the  undissolved  silver  is  concentrated  in  the  residue. 

509633 — November  28,  1893.  D.  K.  TUTTLE  and  C.  WHITEHEAD.  Process  of 
treating  precious  metal-bearing  slimes. — The  process  of  treating  precious  metal- 
bearing  slimes,  which  consists  in  subjecting  the  slimes  to  the  action  of  dilute  acids 
to  dissolve  the  metals  and  oxides  soluble  therein  and  to  the  action  of  a  solution 
of  a  salt  of  silver  to  remove  metals  more  electro-positive  than  silver  that  are  present 
in  the  metallic  state. 

509634 — November  28,  1893.  D.  K.  TUTTLE  and  C.  WHITEHEAD.  Process 
of  refining  slimes  from  the  electrolytic  refining  of  copper.  The  process  of  treating 
slimes  from  the  electrolytic  process  of  refining  copper,  which  consists  in  removing 
arsenic,  antimony,  tellurium,  bismuth,  and  other  impurities  present  as  oxides  by 
treating  the  slimes  with  dilute  acid  and  heating  the  purified  slimes  with  strong 
hydric  sulphate. 

513490 — January  30,  1894.  S.  H.  EMMENS.  Process  of  treating  zinc-lead-sul- 
phide ores. — The  process  of  treating  zinc-lead-sulphide  ores  carrying  gold  or  silver 
or  gold  and  silver,  which  said  process  consists  in,  first,  finely  comminuting  the 
ore;  second,  roasting  the  same  in  an  oxidizing  atmosphere;  thirdly,  leaching 
such  roasted  ore  with  water  containing  ferrous  sulphate;  fourthly,  leaching  such 
once  leached  ore  with  an  aqueous  solution  of  ferrous  and  ferric  sulphates;  fifthly , 
leaching  such  twice  leached  ore  with  water  containing  ferrous  sulphate;  and  sixthly , 
removing  iron  from  the  zinc  sulphate  solution  obtained  by  the  first  and  second 
of  the  said  teachings  by  mixing  such  solutions  together  and  heating  them. 

516016 — March  6,  189 4.  W.  R.  INGALLS  and  F.  WYATT.  Treatment  of  ores 
of  zinc. — The  process  of  treating  ores  of  zinc,  which  consists,  first,  in  subjecting 
the  ore  to  an  oxidizing  roasting;  second,  lixiviating  the  roasted  ore  with  water 
and  sulphuric  acid;  third,  separating  one-fourth  of  the  zinc-sulphate  solution 
thereby  formed  from  the  rest  and  precipitating  the  zinc  from  said  separated  por- 
tion by  means  of  a  sulphide  of  an  alkaline  base;  fourth,  evaporating  the  remainder 
of  the  zinc-sulphate  solution  to  dryness  and  mixing  the  precipitated  sulphide 
therewith;  and  lastly,  heating  the  mixture  in  a  suitable  furnace  whereby  sul- 
phurous anhydride  gas  is  evolved. 

518890 — April  24,  1894.  L.  KLOZ.  Process  of  extracting  zinc  from  ores. — The 
process  of  treating  zinc  ores,  which  consists,  first,  in  the  preparation  of  a  concen- 
trated solution  of  sulphurous  acid;  second,  in  leaching  the  ores  or  furnace  products 


PATENTS  RELATING  TO  CYANIDE   PROCESSES.  337 

with  this  solution  to  form  a  concentrated  zinc  sulphite  solution  free  from  sulphates; 
and  third,  scattering  this  solution  by  steam  to  dispel  the  sulphurous  acid  and 
precipitate  the  zinc  sulphite. 

527473 — October  16,  1894.  P.  ARGALL.  Cyanide  and  chlorination  process  for 
treating  gold-  or  silver-bearing  ores. — In  the  process  of  preparing  gold-  and  silver- 
bearing  ores  for  the  extraction  of  the  precious  metals,  the  improvement  consist- 
ing  in  separating  the  slime  from  the  granulated  ore,  preventing  the  forming  of 
acid  in  the  slime  by  mixing  lime  therewith,  and  then  forming  the  mixture  into 
lumps  for  burning. 

541374 — June  18,  1895.  E.  B.  MIERISCH.  Process  of  extracting  gold  and  silver 
from  their  ores. — The  process  of  extracting  gold  and  silver  from  oxidated  or  roasted 
ores,  which  consists  in  mixing  the  ground  ores  with  sodium  hydrate,  mixed  with 
a  corresponding  quantity  of  calcium  hydrate,  then  subjecting  the  mixture  to  the 
action  of  chlorine,  whereby  the  ores  are  acted  upon  by  chlorates,  and  hydrochlorites 
formed  "in  statu  nascendi,"  and  then  leaching  the  lye  with  a  concentrated  sodium- 
chloride  solution,  the  deterioration  of  which  is  prevented  by  the  addition  of  the 
calcium  hydrate  to  the  sodium  hydrate. 

541447 — June  18,  1895.  H.  F.  WATTS  and  A.  COAN.  Process  of  reducing 
zinc  slimes. — The  process  of  treating  zinc  slimes  containing  the  precious  metals, 
which  consists  in  first  treating  the  same  with  dilute  sulphuric  acid  for  the  pur- 
pose of  removing  metallic  zinc,  washing  the  residue  to  remove  the  soluble  salts 
and  the  remaining  acid,  and  boiling  the  residue  thus  formed  with  concentrated 
sulphuric  acid  to  dissolve  the  cyanide  of  zinc  and  the  other  salts  thereof  which 
are  insoluble  in  the  dilute  acid. 

541659 — June  25,  1895.  J.  J.  CROOKE.  Process  of  and  apparatus  for  extracting 
silver  from  its  ores. — The  process  of  extracting  silver  from  its  ores,  which  con- 
sists in  roasting  the  ores  with  chloride  of  sodium,  treating  the  roasted  mass  with 
a,  hot  aqueous  solution  containing  chloride  of  sodium,  nitrate  of  copper,  and  sul- 
phuric acid,  and  recovering  the  silver  from  the  solution. 

544499 — August  13,  1895.  H.  BREWER.  Process  of  utilizing  waste  lye. — The 
process  of  treating  zinciferous  or  cupriferous  lyes  resulting  from  the  lixiviation 
of  chlorinated  roasted  ores,  which  consists  in  chemically  extracting  the  metals 
in  the  lye,  except  the  zinc,  removing  the  sodium  chloride  by  concentration  of  the 
lye,  extracting  the  zinc  and  chlorine  from  the  remaining  lye  electrolytically,  and 
effecting  the  chemical  extraction  in  such  manner  that  the  final  lye  will  consist 
essentially  of  a  solution  of  calcium  chloride. 

544612 — August  13,  1895.  A.  CROSSLEY.  Process  of  manufacturing  zinc. — The 
process  for  the  manufacture  of  zinc  oxide,  which  consists  in  adding  sulphuric  acid 
to  the  metallic  ores  or  compounds,  heating  the  mixture  and  converting  the  lead 
present  to  an  insoluble  salt,  and  depositing  any  silver  or  gold  present,  then  diluting 
with  water  and  converting  the  other  metals  present  to  soluble  salts,  filtering  off 
the  clear  liquor,  then  treating  the  clear  acid  liquor  filtered  off  with  an  alkaline 
sulphi.de,  precipitating  the  copper  as  copper  sulphide,  then  filtering  the  liquor 
from  the  precipitate,  treating  with  an  alkali  until  neutral,  passing  chlorine  into 
it  until  all  manganese  and  iron  present  form  manganic  and  ferric  oxides,  which 
are  thrown  down  by  a  slight  excess  of  alkali,  adding  an  excess  of  alkali  to  bring 
the  zinc  oxide  into  solution,  and  then  precipitating  the  zinc  oxide,  and  filtering 
off  the  liquor  therefrom. 

547587 — October  8,  1895.  C.  V.  PETRAEUS.  Method  of  extracting  zinc  from 
complex  ores. — The  method  of  separating  zinc  from  complex  ores  where  it  is  found 
as  a  sulphate  or  sulphite,  which  consists  in  crushing  the  ore,  roasting  it,  dissolving 
out  the  soluble  zinc  salts  in  water,  adding  a  solution  of  sulphuric  acid  to  dissolve 
out  any  zinc  oxide,  introducing  live  steam  to  the  mixture  of  ore  and  solvents  to 
thoroughly  mix  and  heat  them,  separating  the  solution  of  sulphate  of  zinc  from 
the  insoluble  parts  of  t'.e  ore,  adding  chloride  of  calcium  to  the  solution  to  con- 
vert the  zinc  into  a  chloride,  separating  the  solution  of  zinc  chloride  from  the  pre- 
cipitated calcium  sulphate  and  finally  adding  quicklime  to  the  solution  of  zinc 
chloride  to  precipitate  the  zinc  as  zinc  oxide. 

556690 — March  17,  1896.  G.  O.  PEARCE.  Process  of  extracting  gold  from 
solutions. — The  process  of  recovering  gold  and  platinum  metals  from  aqueous 


338  APPENDIX. 

solutions  of  these  metals,  which  consists  in  passing  said  solutions  through  a  mass 
of  vegetable  carbon  having  associated  with  it  sulphate  of  iron,  oxalic  acid,  and 
tartaric  acid. 

559614 — May  5,  1896.  G.  A.  SCHROTER.  Extraction  of  precious  metals. — The 
process  of  extracting  precious  metals,  particularly  silver,  from  ores  and  metal- 
lurgical products,  which  consists  in  leaching  the  crushed  and  chloridized  ore  with 
a  concentrated  solution  of  brine  to  which  has  been  added  a  small  per  cent  (one- 
half  to  4  per  cent,  approximately)  of  a  soluble  salt  of  copper. 

561544 — June  2,  1896.  F.  P.  DEWEY.  Process  of  treating  sulphides. — The 
process  of  treating  mixtures  containing  sulphides  of  silver  and  copper,  which  con- 
sists in  heating  the  mixture  with  strong  sulphuric  acid,  adding  water,  adding  more 
mixed  sulphides,  separating  the  solution  of  sulphate  of  copper  from  the  residue 
containing  the  sulphide  of  silver,  and  heating  the  sulphide  of  silver  with  strong 
sulphuric  acid  to  convert  it  into  sulphate. 

561571 — June  9,  1896.  F.  P.  DEWEY.  Process  of  treating  mixtures  containing 
sulphides. — The  process  of  treating  mixtures  containing  sulphides  of  silver  and 
copper,  which  consists  in  heating  them  to  a  temperature  at  which  the  sulphur 
is  oxidized,  in  an  excess  of  sulphuric  acid  sufficient  to  convert  the  sulphides  of 
silver  and  copper  into  sulphates,  and  bring  the  sulphate  of  silver  into  solution 
outside  of  the  mass  of  material  treated,  thereby  oxidizing  the  sulphur,  converting 
the  sulphides  into  sulphates,  and  bringing  the  sulphate  of  silver  into  solution  in 
the  acid  outside  of  the  mass  of  material  acted  upon. 

571369 — November  17,  1896.  B.  HUNT.  Process  of  refining  gold  and  silver 
bullion. — The  process  of  refining  bullion  slimes  by  first  roasting  the  slimes  to  decom- 
pose all  cyanogen  compounds  and  carbonaceous  matters  and  then  treating  the 
roasted  slimes  with  nitric  acid. 

586159 — July  13,  1897.  H.  BREWER.  Process  of  treating  zinc  sulphide  ores. — 
In  a  process  of  treating  zinciferous  sulphate  lyes  resulting  from  the  lixiviation 
of  chlorinated  roasted  zinc  sulphide  ores,  adding  sodium  chloride  to  such  lye  to 
saturation  or  in  excess,  and  crystallizing  out  the  resulting  sodium  sulphate  (Glauber 
salt)  by  refrigeration  as  a  by-product. 

587128 — July  27,  1897.  E.  F.  TURNER.  Process  of  treating  argentiferous  sul- 
phide ores. — In  a  process  for  the  extraction  of  the  metal  of  compound  sulphide 
ores,  disintegrating  and  decomposing  the  latter  by  the  combined  action  of  aqueous 
and  gaseous  hydrochloric  acid,  neutralizing  the  acid  gases  evolved  whereby  sul- 
phureted  hydiogen  is  obtained,  heating  the  disintegrated  ore  by  means  of  such 
sulphureted  hydrogen,  collecting  the  sulphur  dioxide  resulting  from  the  combus- 
tion, bringing  this  gas  into  contact  with  sodium  chloride  in  presence  of  heat,  whereby 
hydrochloric  acid  gas  and  sodium  sulphate  are  obtained,  and  utilizing  the  former 
in  the  process  of  disintegration. 

588476 — August  17,  1897.  H.  A.  RHODES.  Process  of  separating  gold  and 
silver  or  other  precious  metals  from  their  ores. — In  chemical  processes  for  the  separa- 
tion of  gold  or  other  precious  metals  from  their  ores,  slimes,  or  compounds,  the 
method  of  preparing  the  ores  by  adding  thereto  a  self-hardening,  binding  mate- 
rial and  forming  a  porous  and  rigid  mass  of  the  compound  whereby  the  precious 
metals  contained  therein  are  freely  acted  upon  by  the  solvent. 

589959 — September  14,  1897.  J.  J.  CROOKE.  Process  of  treating  copper  sul- 
phides.— The  process  of  recovering  silver  or  gold  and  extracting  copper  in  a  metallic 
condition  from  copper  sulphides  associated  with  iron  sulphides,  which  consists 
in  roasting  the  pulverized  sulphides  with  sodium  chloride  at  a  low  heat,  leaching 
the  roasted  mass  with  a  solution  whereby  the  iron  sulphides  are  largely  converted 
into  oxides  and  the  silver  and  gold  are  dissolved  by  and  removed  with  the  solu- 
tion, recovering  the  silver  and  gold  from  the  solution,  roasting  the  residuum  or 
tailings,  fluxing  the  rcasted  tailings  with  silica  and  pulverized  carbon,  gradually 
melting  the  roasted  and  fluxed  charge  to  convert  the  oxide  of  iron  into  metallic 
iron  and  desulphurize  the  copper  sulphides  to  liberate  metallic  copper  and  form 
an  iron  silicate  slag,  removing  the  slag  from  the  melted  copper,  adding  a  small 
per  centum  of  silica  to  convert  any  remaining  iron  oxide  or  metallic  iron  into  an 
iron  silicate  slag,  and  removing  this  slag  from  the  copper. 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  339 

602295 — April  12,  1898.     E.  A.  ASHCROFT.     Treating  solutions  or  ores  contain- 
ing zinc  for  recovering  zinc  as  oxides. — The  process  of  treating  neutral  zinc  solu- 
tions for  the  production  of  zinc  oxide,  which  consists  in  first  converting  the  neutral        » 
zinc  salt  into  basic  zinc  salt  by  the  addition  of  zinc  oxide  and  then  intimately   \/ 
mixing  with  said  basic  zinc  salt,  carbon  in  approximately  the  proportion  of  one-   ' 
twentieth  of  the  weight  of  the  zinc  to  be  recovered,  and  heating  the  mixture  to 
a  temperature  approximately  the  melting-point  of  aluminum. 

623154 — April  18,  1899.  H.  HOWARD.  Extraction  of  zinc  and  copper  from 
ores. — The  process  of  extracting  zinc  and  copper  from  ore  or  residue,  which  con- 
sists in  treating  the  same  with  aqua  ammonia  and  ammonium  sulphate ;  separating 
the  copper  from  the  resulting  solution;  adding  sufficient  soda  to  combine  with 
all  of  the  sulphuric  oxide  present  and  form  sulphate  of  soda,  and  evaporating  the 
solution  to  drive  off  ammonia,  the  latter  being  collected  in  water;  and  treating 
the  residue  with  water  to  dissolve  out  the  sulphate  of  soda,  the  zinc  oxide  remaining. 

624000 — May  2, 1899.  J.  DURIE.  Method  of  reducing  metallic  sulphides. — In  the 
process  of  causing  the  solution  of  metallic  sulphides  containing  lead,  subjecting  the 
sulphide  ore  to  a  solution  of  sulphuric  acid  and  a  nitrate  of  an  alkali  metal  at  a  tem- 
perature of  about  212°  Fahrenheit,  washing  and  filtering  the  lead  sulphate  obtained 
therefrom,  dissolving  the  said  sulphate,  precipitating  by  carbon  dioxide,  wash- 
ing, and  drying  the  precipitated  hydrated  carbonate  of  lead,  and  recovenng  the 
sulphur. 

625433 — May  23,  1899.  M.  BODY.  Process  of  treating  sulphureted  ores. — In 
the  process  of  treating  sulphureted  ores  of  a  complex  nature,  comminuting  and  I 
melting  the  ore  in  presence  of  an  alkaline  salt  and  carbon,  whereby  alkaline  poly-  I 
sulphides  soluble  in  water  are  formed,  plunging  the  melted  mass  into  water,  whereby 
a  magnetic  precipitate  is  formed  and  the  polysulphides  dissolved  in  the  water, 
separating  the  solution  from  the  precipitate,  subjecting  the  same  to  the  action 
of  air  and  sulphurous-acid  gas  forced  thereinto,  whereby  monosulp hides  of  iron, 
together  with  the  precious  metals,  are  precipitated,  maintaining  the  alkalinity 
of  the  solution  during  the  operation  of  precipitation  by  addition  of  an  alkaline 
substance,  as  lime,  separating  the  solution  from  the  monosulphide-of-iron  pre- 
cipitate, extracting  from  the  latter  the  copper  and  then  the  precious  meatl,  and 
separating  the  arsenic  and  antimony  from  the  solution  by  precipitation 

627024 — June  13,  1899.  R.  THRELFALL.  Method  of  treating  flue  dust  and 
fume  obtained  from  sulphide  ores. — In  the  treatment  of  flue  dust  and  fume  from 
sulphide  ores,  the  separation  of  the  zinc  from  the  lead  constituents  by  leaching 
out  the  former  by  means  of  a  solution  of  alkali  metal  hydrogen  sulphate, 

630951 — August  15,  1899.     L.  VANINO.     Wet  process  of  extracting  silver  from 
its  haloid  salts. — The  wet  process  of  extracting  silver  from  its  insoluble   haloid      » 
salts,  which  consists  in  mixing  said  haloid  salts  with  a  watering  solution  of  alka-       *•* 
line  agents,  and  adding  formic  aldehyde  in  the  cold. 

635056 — October  17,  1899.     D.  O'KEEFE.     Process  of  treating  ore.— The  process 
of  treating  ore,  consisting  of  roasting  the  same  while  being  agitated,  for  the  pui-       ^ 
pose  of  mechanical  disintegration,  subjecting  the  ore  to  hydrogen  gas  under  pres- 
sure, afterwards  to  chlorine  gas,  and  then  leaching  the  same  with  hot  salt  water. 

635695 — October  24,  1899.  C.  MARTIN.  Process  of  chemically  preparing  and 
treating  rebellious  ores. — The  process  of  effecting  the  separation  of  gold,  silver, 
tin,  lead,  and  platinum,  in  pulverized  rebellious  ore  containing  arsenic  and  anti- 
mony, which  consists  in  effecting  sulphurization  and  disintegration  of  the  said 
ore,  producing  a  sulphide  solution  of  the  metals  in  said  ore,  and  thereupon  pre- 
cipitating the  dissolved  metallic  compounds  other  than  arsenic  and  antimony 
by  mingling  the  same  with  an  oxide  of  an  alkali  earth  metal. 

635793 — October  31,  1899.     F.  W.  MARTINO  and  F.  STUBBS.     Process  of  treat- 
ing ores  containing  pr^ious  metals. — The  treatment  of  ores  or  tailings  containing 
the  precious  metals  by  finely  dividing  the  ore,  mixing  it  with  calcium  carbide,       ^ 
and  moistening  the  mixture  with  water. 

644770 — March  6,  1900.  R.  W.  KENNEDY.  Solvent  for  leaching  ores. — A 
solvent  for  leaching  ores,  comprising  sodium  thiosulphate,  ammonium  carbonate, 
copper  sulphate,  and  potassium  cyanide  in  water. 


340  APPENDIX 

647989— April  24,  1900.  T.  RYAN,  Jr.,  and  N  HUGHES  Process  of  extracting 
vine  from  substances  containing  same. — The  process  of  extracting  zinc  from  sub- 
stances containing  the  same,  consisting  in  subjecting  the  raw  material  to  the  action 
of  a  solution  of  a  caustic  alkali,  precipitating  any  lead  present  by  galvanic  action, 
securing  the  removal  of  organic  matters  and  iron,  manganese,  and  silicon  by  the 
addition  of  caustic  lime  and  bleaching-powder,  and  finally  precipitating  the  dis- 
solved zinc  in  the  form  of  zinc  oxide  or  zinc  hydroxide  by  decaustifying  the  solu- 
tion by  the  addition  of  an  acid. 

648354 — April  24,  WOO.  C.  G.  COLLINS.  Process  of  extracting  metals  from 
their  ores. — The  process  of  extracting  metals  from  their  ores,  consisting  in  dis- 
solving out  or  extracting  the  metal  from  the  powdered  ore  by  means  of  a  solution 
of  ammonium  salt  in  the  presence  of  an  alkali  base  capable  of  decomposing  the 
ammonium  salt,  and  then  precipitating  the  metal  by  the  addition  of  a  solution 
of  an  alkali  metal. 

652072 — June  19,  1900.  G.  DE  BECHI.  Treatment  of  ore.— The  method  of 
treating  complex  ores,  consisting  in  subjecting  the  ore  to  a  chloridizing  roasting, 
condensing  the  vapors  and  gases  evolved,  treating  the  roasted  ore  and  the  acidu- 
lated water  containing  the  condensed  vapors  and  gases  with  calcium  chloride 
to  precipitate  soluble  sulphates  and  sulphuric  acid  as  insoluble  calcium  sulphate, 
then  lixiviating  the  ore  with  the  acidulated  water  to  obtain  a  solution  of  zinc  and 
copper  salts  and  fractionally  precipitating  zinc  and  copper  from  the  said  solution 
as  hydrated  oxides  by  successive  additions  of  lime. 

652849 — July  3,  1900.  S.  H.  JOHNSON  and  H.  L.  SULMAN.  Process  of  extract- 
ing metals  from  ores  or  slimes. — The  method  of  treating  pressed  slime  cakes  con- 
taining residual  water,  which  consists  in  displacing  the  residual  water  with  an 
equal  volume  of  a  solvent  solution,  mixing  the  cakes  with  a  further  quantity  of 
solvent  solution,  removing  the  metal-bearing  solvent  solution  by  pressure,  dis- 
placing the  remaining  portion  of  such  metal-bearing  solution  with  water  and  extract- 
ing the  metal  from  said  mteal-bearing  solution,  whereby  all  the  operations  may  be 
performed  with  an  approximately  constant  volume  of  the  solvent  solution. 

653414 — July  10,  1900.  E.  FINK.  Process  of  extracting  copper  or  other  metals 
from  tailings  or  ores  of  such  metals. — The  process  of  extracting  copper  and  other 
metals  from  tailings  or  ores  of  such  metals,  which  consists  in  subjecting  the  tail- 
ings or  ore  to  the  action  of  a  solution  containing  sulphuric  acid  and  to  the  action 
of  an  oxide  or  oxides  of  nitrogen  in  the  presence  of  air  or  oxygen  under  pressure, 
whereby  the  metal  is  oxidized  and  dissolved  and  the  oxide  or  oxides  of  nitrogen 
are  converted  alternately  into  a  lower  and  a  higher  oxide  or  oxides,  and  finally 
separating  the  solution  from  the  earthy  matter  of  the  tailings  or  ore  and  sepa- 
rating the  metal  from  the  solution. 

654804 — July  31,  1900.  G.  RIGG.  Process  of  obtaining  oxide  and  carbonate 
of  zinc  from  materials  containing  zinc. — The  process  of  producing  oxide  of  zinc  and 
carbonate  of  zinc  from  zinciferous  material,  which  consists  in  leaching  the  zincifer- 
ous material  with  a  solution  of  ammonia  and  carbon  dioxide  wherein  the  carbon 
dioxide  is  in  such  proportion  to  the  ammonia  as  to  impart  to  the  latter  an  approxi- 
mately maximum  zinc  dissolving  capacity. 

656497 — August  21,  1900.  G.  DE  BECHI.  Process  of  treating  zinc-bearing  com- 
plex ores  for  recovery  of  zinc  or  other  metals  therefrom. — The  method  of  treating  com- 
plex zinc  ores  for  the  recovery  therefrom  of  copper,  zinc,  and  lead,  consisting  in 
separately  roasting  the  ore  and  an  alkali  chloride  in  the  presence  of  air  and  steam, 
conveying  the  sulphurous  and  sulphuric  vapors  thus  derived  from  the  ore  over 
and  in  contact  with  the  said  chloride  during  the  roasting:  to  obtain  hydrochloric 
acid  fumes,  condensing  the  acid  fumes,  lixiviating  the  roasted  ore  with  the  acid 
liquor  thus  obtained  to  produce  a  solution  of  metallic  chlorides,  and  successively 
precipitating  the  metals  of  the  metallic  chlorides  as  hydrates  by  successive  addi- 
tions of  alkali. 

656544 — August  21,  1900.  H.  HIRSCHING.  Process  of  treating  gold  and  silver 
ores. — The  process  of  treating  copper  ores,  which  consists  in  adding  the  com- 
mintued  ore  gradually  under  agitation  to  an  ammoniated  solution,  and  then  adding 
a  diluting  liquid  to  the  mixture  to  obtain  a  highly  concentrated  copper  solution. 


PATENTS  RELATING  TO    CYANIDE  PROCESSES.  341 

657955 — September  18,  1900.  H.  PETERSEN.  Process  of  enriching  metallic 
sulphides. — The  process  of  enriching  metallic  sulphides,  which  are  mixed  with 
carbonates  of  the  alkali  earth  metals,  consisting  hi  dissolving  out  the  carbonates 
with  an  aqueous  solution  of  sulphurous  acid. 

659338 — October  9,  1900.  C.  G.  COLLINS.  Process  of  extracting  zinc  and  cop- 
per from  their  ores. — The  process  of  treating  ores  'of  copper  and  zinc,  which  con- 
sists in  immersing  the  comminuted  ore  in  a  solution  containing  sodium  sulphate 
and  bisulphate  (niter  cake),  removing  the  depleted  ore  and  extracting  the  metal 
therefrom  by  electrolytic  action,  adding  more  comminuted  ore  to  the  remaining 
solution,  and  repeating  the  operation. 

659339 — October  9,  1900.  C.  G.  COLLINS.  Process  of  extracting  copper  and 
zinc  from  their  ores. — The  process  of  treating  ores  of  copper  and  zinc  containing 
other  metals  soluble  in  any  excess  of  solution  which  may  be  employed  above  that 
required  to  dissolve  the  copper  and  zinc  contained  therein,  which  consists  in  intro- 
ducing the  comminuted  ore  into  a  solution  of  sodium  sulphate  containing  hydro- 
chloric and  sulphuric  acid  (salt-cake  solution)  not  exceeding  5°  Baume,  and  sub- 
sequently recovering  these  metals  from  the  solution. 

.  659670— October  16,  1900.  C.  J.  HEAD  and  R.  C.  WILD.  Method  of  treating 
telluride  ores. — A  process  for  the  extraction  of  tellurium  from  telluride  aurifer- 
ous ores  and  the  preparation  thereby  of  said  ores  or  the  better  extraction  of  the 
precious  metal  therefrom,  consisting  of  a  lixiviation  and  digestion  of  the  said  ores 
in  a  solution  containing  about  5  per  cent,  of  caustic  potash  or  soda  for  a  lengthened 
period  of  fcwo  to  six  hours,  the  withdrawal  of  the  solution  after  such  digestion 
from  the  said  ores,  and  the  recovery  of  the  tellurium  from  the  solution. 

660013— October  16,  1900.  C.  J  HEAD  and  R.  C.  WILD.  Method  of  treating 
telluride  ores. — A  process  for  the  extraction  of  tellurium  from  telluride  auriferous 
ores  and  the  preparation  thereby  of  said  ores  for  the  better  extraction  of  the  precious 
metal  therefrom,  consisting  of  a  lixiviation  and  digestion  of  the  said  ores  in  a  solu- 
tion  containing  about  5  per  cent,  of  carbonate  of  sodium  or  potassium  for  a  lengthened 
period  of  two  to  six  hours,  the  withdrawal  of  the  filtrate,  and  the  recovery  of  the 
tellurium  from  the  solution. 

663759 — December  11,  1900.  C.  HOEPFNER.  Process  of  producing  solutions 
of  zinc  chloride. — The  process,  which  consists  in  reacting  upon  an  oxide  or  insoluble 
salt  of  zinc  in  presence  of  water  with  sulphurous  acid  to  form  soluble  zinc  bisulphite 
converting  the  bisulphite  into  a  monosulphite  by  suitable  reagents,  mixing  there- 
with its  equivalent  of  sodium  or  potassium  chloride  and  exposing  the  mixture  to 
heat  and  air  in  the  presence  of  a  contact  substance,  such  as  oxide  of  iron,  in  order 
to  convert  the  monosulphite  into  a  sulphate,  separating  the  zinc  chloride  from 
the  solution  and  mixing  therewith  a  sufficient  quantity  of  an  aqueous  solution 
of  sodium  chloride  to  dissolve  the  zinc  chloride  and  leave  the  alkali-metal  sulphate 
practically  undissolved. 

678210 — July  9,  1901.  J.  W.  WORSEY.  Process  of  treating  complex  ores. — 
Process  for  the  treatment  of  complex  sulphide  ores,  comprising,  first,  the  reduc- 
tion of  the  combined  sulphur  below  15  per  cent,  by  calcination;  secondly,  finely 
powdering  the  calcined  ore;  thirdly,  adding  sodium  nitrate;  fourthly,  boiling 
the  mixed  ore  and  nitrate  in  dilute  sulphuric  acid;  fifthly,  roasting  the  semisolid 
mass  in  a  closed  furnace;  sixthly,  dissolving  out  zinc  copper  and  other  soluble  salts 
from  the  said  mass  by  weak  sodium-sulphate  solution;  seventhly,  removing  any 
copper  from  the  solution;  eighthly,  precipitating  the  zinc  and  other  metals  from 
the  solution;  and,  ninthly,  separating  the  zinc. 

679215 — July  23,  1901.  H.  C.  BULL.  Method  of  extracting  gold  from  sea-water. — 
The  method  of  extracting  gold  from  sea-water,  which  consists  in  mixing  with  a 
quantity  of  sea-water  a  proportion  of  milk  of  lime  to  react  upon  the  iodide  of  gold 
contained  in  the  sea-water  to  form  iodide  of  calcium  and  to  liberate  the  gold,  then 
allowing  the  sludge  formed  by  the  reaction  to  settle,  then  drawing  off  the  water 
.and  then  collecting  the  sludge  and  treating  it  to  extract  the  metallic  gold  therefrom. 

683325 — September  24,  1901.  H.  J.  PHILLIPS.  Extraction  of  precious  metals 
from  their  ores. — The  method  of  extracting  precious  metals  from  refractory  sul- 
phide or  telluride  ores  without  roasting,  which  consists  in  subjecting  the  ore  with- 


342  APPENDIX. 

out  roasting  and  in  the  form  of  a  powder,  under  heat  and  pressure,  to  the  action 
of  alkaline  polysulphides  in  solution  of  such  weakness  that  same  will  have  a  selec- 
tive action,  namely,  will  dissolve  the  elements  which  are  combined  with  the  gold, 
and  for  which  the  polysulphides  have  a  greater  affinity  than  for  gold,  without 
dissolving  the  gold  itself,  which  latter  is  thus  dissociated  and  can  then  be  recovered 
by  any  known  suitable  process  for  recovering  free  gold. 

684578 — October  15,  1901.  C.  W.  MERRILL.  Precipitant  for  recovering  metals 
from  solutions. — The  combination  with  a  metal  capable  of  precipitating  other 
metals  from  cyanide  solutions,  if  a  gritty,  inert,  non-metallic  material,  to  increase 
the  surface  exposed  per  unit  of  weight  of  the  precipitating  metals. 

689835 — December  24,  1901.  G.  H.  WATERBURY.  Process  of  extracting  copper 
from  ores. — The  process  of  precipitating  copper  in  solution,  consisting  in  placing 
the  solution  in  a  tank  or  receptacle  containing  pieces  of  iron  small  enough  to  allow 
the  solution  to  pass  readily  therethrough,  and  introducing  hot  air  under  pressure 
into  the  solution. 

692008— January  28,  1902.  O.  FROLICH,  M.  HUTH,  and  A.  EDELMANN.  Sepa- 
rating process  for  ores. — In  the  art  of  separating  metals  from  ores  containing  iron 
among-  a  plurality  of  metals  existing  therein  in  a  combined  form,  the  process, 
which  consists  in  heating  the  ore  to  a  temperature  below  the  decomposition  tem- 
perature of  the  sulphate  of  the  metal  to  be  sulphated,  but  above  the  decomposing 
temperature  of  the  sulphate  of  any  other  metal  existing  in  the  ore,  and  then  pass- 
ing over  it  a  gas  mixture  containing  sulphur  dioxide  and  oxygen. 

693148 — February  11,  1902.  E.  B.  PARNELL.  Process  of  treating  ores. — In'  the 
treatment  of  refractory  ores,  the  process,  which  consists  in  subjecting  them  to 
the  action  of  chromic  acid  and  then  roasting  them. 

695306 — March  11,  1902.  M.  M.  HAFF.  Separation  of  the  constituents  of  com- 
plex sulphide  ores. — The  process,  which  consists  in  heating  mixed  sulphides  of  zinc 
and  lead  with  sulphate  of  an  alkali  metal,  treating  the  resultant  mass  with  a  dis- 
solving agent  to  dissolve  the  zinc  sulphate  and  alkali -metal  sulphate,  while  leaving 
the  lead  sulphate  undissolved,  and  adding  barium  hydrate  to  the  mixed  solu- 
tion of  zinc  sulphate  and  alkali-metal  sulphate  to  precipitate  zinc  hydrate  and 
barium  sulphate. 

699326 — May  6,  1902.  T.  A.  IRVINE.  Extraction  of  copper  by  the  wet  method. — 
A  process  for  the  extraction  of  copper,  consisting  in  the  treatment  of  the  ore  within 
a  mixed  solution  of  chloride  of  sodium  and  sulphuric  acid,  in  which  solution  there 
is  an  excess  by  weight  of  the  chloride  of  sodium  in  respect  to  the  sulphuric  acid. 

700311 — May  20,  1902.  F.  ELLERHAUSEN.  Treatment  of  complex  and  refrac- 
tory ores. — The  process  of  treating  complex  and  refractory  ores  containing  lead, 
silver,  and  zinc,  which  consists  in  smelting  the  raw  ores,  churning  the  fumes  and 
gases  with  water  to  condense  and  mix  them  with  water,  settling  out  the  lead,  sil- 
ver, and  part  of  the  zinc  compounds  from  the  resulting  liquor,  as  a  sludge,  sepa- 
rating and  drying  the  sludge  and  fusing  the  sludge  with  caustic  alkali,  thereby 
precipitating  the  lead  in  metallic  form. 

702047 — June  10,  1902.  C.  G.  COLLINS.  Process  of  rendering  metallic  sul- 
phides soluble. — The  process  of  rendering  metallic  sulphides  soluble,  consisting 
m  drenching  the  crushed  sulphide  ore  with  aqueous  ammonia,  draining  off  the 
excess  of  aqueous  ammonia,  treating  the  ore  thus  moistened  to  an  excess  of  oxygen, 
leaching  the  ore,  and  repeating  the  operation  until  the  metal  is  all  extracted  from 
the  pulp. 

702153 — June  10,  1902.  J.  P.  VAN  DER  PLOEG.  Treatment  of  ores  and  mate- 
rials containing  antimony. — The  method  of  extracting  antimony  from  ores,  mate- 
rials, or  residues  containing  it,  consisting  in  finely  pulverizing  the  material,  mixing 
it  with  a  suitable  quantity  of  powdered  quicklime,  and  then  mixing  with  it  an 
adequate  quantity  of  sulphide  of  an  alkali-earth  metal  and  water,  so  as  to  form 
a  solution  of  the  lower  and  most  soluble  double  sulphides  as  being  the  best  elec- 
trolytes, without  the  use  of  artificial  heat  or  application  of  pressure. 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.       343 

702244. — June  10,  1902.  A.  J.  POLMETEER.  Precipitant  for  treatment  of  cop- 
per-water.— The  precipitant  for  copper-water,  containing  in  solution  a  sulphide 
and  an  excess  of  alkali. 

702582— June  17,  1902.     J.  W.  NEILL  and  J.  H.  BURFEIND.     Process  of  recwer- 
ing  metals  from  ores. — The  improvement  in  treating  copper  or  other  ores,  consisting 
in  agitating  a  charge  of  pulp  containing  the  ore  by  gas  from* roasting  furnaces    v      , 
charged  with  material  suitable  for  producing  sulphurous-acid  gas,  separating  the  Vy' 
resultant  solution,  precipitating  the  metal  from  the  solution    thereby  releasing;'/^ 
gas  and  employing  the  sulphurous-acid  gas  released  by  the  precipitating  process 
to  enrich  the  gas  derived  from  the  furnace  and  used  in  leaching  a  charge  of  ore. 

704640 — July  -15,  1902.  C.  HOEPFNER.  Process  of  extracting  copper  and 
nickel  from  sulphide  compounds. — The  process,  which  consists  in  oxidizing  roast- 
ing copper  and  nickel  sulphide  ores  or  mattes,  leaching  the  sulphate  of  copper 
formed,  converting  this  into  cupric  chloride  and  then  into  cuprous  chloride,  dis- 
solving the  nickel  salts  in  the  residue  by  said  cuprous  chloride,  precipitating  cup- 
rous chloride  from  the  solutions  formed  and  returning  the  resulting  solution  con- 
taining some  cuprous  chloride  into  the  cycle  of  operations. 

704641 — July  15,  1902.  C.  HOEPFNER.  Process  of  extracting  zinc  or  other- 
metals  from  their  ores. — The  process  which  consists  in  reacting  on  a  material  con- 
taining an  oxygen  compound  of  metals  insoluble  in  water  and  whose  chlorides- 
are  soluble  in  a  solution  of  alkali  metal  chloride,  with  sulphurous  acid  and  an  aque- 
ous solution  of  alkali  metal  chloride,  whereby  a  solution  is  formed  containing  a 
chloride  of  a  metal. 

706302 — August  5,  1902.  L.  B.  DARLING.  Means  for  extracting  precious 
metals  from  ores. — In  a  gold-extracting  plant  provided  with  a  substantially  flat 
treating  floor  of  non-absorbent  material,  a  series  of  longitudinally  extending  chan- 
nels formed  therein,  a  transverse  groove  or  end  launder  in  direct  communication 
with  said  channels,  fixed  screens  or  strainers  covering  the  top  of  said  channels  and 
launder,  side  launders  or  ducts,  and  valved  connections  interposed  between  and 
uniting  the  said  end  and  side  launders. 

707107 — August  19,  1902.  J.  HERMAN.  Process  of  treating  ores. — The  process 
which  consists  in  roasting  sulphide  of  copper  ore  at  a  low  heat  to  form  sulphates 
of  the  copper  and  some  of  the  iron  present,  and  produce  a  large  percentage  of  fer- 
rous sulphate,  leaching  the  roasted  ore,  precipitating  the  metallic  copper,  and 
adding  salt  to  the  leaching  solution  before  or  after  the  precipitation  of  the  metallic 
copper,  whereby  the  ferrous  salts  in  the  solution  are  converted  to  the  chloride f 
and  a  solution  having  an  excess  of  salt  is  produced,  and  the  said  solution  is  adapted 
to  dissolve  copper  and  silver  out  of  carbonate  and  oxide  ores. 

707506 — August  19,  1902.  E.  FERRARIS.  Method  of  treating  mixed  sulphide 
ores. — The  process  of  decomposing  mixed  sulphide  ores  by  means  of  concentrated 
sulphuric  acid  without  the  aid  of  extraneous  heat. 

709037 — September  16,  1902.  W.  PETHYBRIDGE.  Treatment  of  telluride  gold 
ores. — In  the  decomposition  of  ores  containing  telluride  of  gold,  the  process  of 
reducing  the  ore  to  a  finely  divided  state  and  then  exposing  the  ore  to  the  action 
of  a  solution  of  ferric  chloride  alone  to  attack  the  tellurium. 

715023 — December  2,  1902.  J.  C.  CLANCY  and  L.  W.  MARSLAND.  Process 
of  treating  zinc  sulphide  ores. — In  extracting  metals  from  zinciferous  sulphide  ores, 
roasting  pulverized  ores  with  the  addition  or  admixture  of  lead  sulphate  obtained 
from  a  source  external  to  the  ore  being  treated  in  quantity  proportional  to  the 
quantity  of  zinc  the  ore  contains. 

715771— December  16,  1902.  F.  ELLERHAUSEN  and  R.  W.  WESTERN.  Treat- 
ment of  zinc  ores. — The  process  for  the  treatment  of  zinc  ores  and  other  zinciferous 
matter,  consisting  in  calcining  where  necessary,  wetting  with  a  dilute  solution 
of  ammonium  sulphate,  adding  sulphuric  acid,  washing  with  ammonium  sulphate , 
and  precipitating  with  aqueous  ammonia  and  heating  the  precipitate. 

715804 — December  16,  1902.  H.  E.  HOWARD  and  G.  HADLEY.  Treatment  of 
spent  acid  from  galvanizing  works. — The  treatment  of  spent  acid  from  galvanizing 
works  by  adding  zinc  thereto,  separating  the  solution  from  the  precipitate,  treat- 


344  APPENDIX. 

ing  with  bleaching  powder  to  transform  the  ferrous  salts  into  ferric  salts,  then 
adding  alkali  to  precipitate  the  iron  present  as  ferric  hydrate,  and  subsequently 
more  alkali  for  the  precipitation  of  the  zinc  salts. 

71684? — December  23,  1902.  F.  W.  MARTINO.  Treatment  of  ores  containing 
precious  metals. — The  process  of  separating  gold  from  ores  containing  tellurium, 
r  selenium,  sulphur,  arsenic,  antimony,  tin,  phosphorus,  or  the  like,  consisting  in 
grinding  the  mixture,  heating  it  with  powdered  barium  sulphocarbide  in  a  reduc- 
ing (muffle)  furnace,  dissolving  out  the  soluble  sulphides  thus  formed,  treating 
the  solid  residue  with  a  gold  solvent,  and  precipitating  the  gold  therefrom  by  the 
employment  of  barium  sulphocarbide. 

717299— -December  30,  1902.  G.  C.  STONE.  Extraction  of  zinc  and  lead  from 
sulphide  ores. — The  method  of  separating  zinc  and  lead  from  sulphide  ores,  which 
consists  in  smelting  the  sulphides,  oxidizing  the  volatile  constituents  at  their  exit 
from  the  smelting  furnace,  cooling  the  resulting  fumes  and  products  of  combus- 
tion to  a  temperature  not  exceeding  180°  F.,  and  passing  them  into  contact  with 
a  solvent  which  will  dissolve  out  one  of  the  metals  and  not  the  other. 

717565 — January    6,    1903.     A.    VON    GERNET.     Process    of    extracting   copper 
from  its  ores. — The  process  of  extracting  copper  from  its  ore,  which  consists  in 
^X.        slowly  passing  the  ore  in  the  form  of  pulp  through  a  current  of  sulphurous  acid, 
passed  in  a  direction  opposite  to  that  of  the  travel  of  the  pulp. 

7 17 86 4— January  6,  1903.  J.  T.  JONES.  Method  of  treating  ores. — The  process 
of  mixing  with  ore,  to  be  treated,  a  leaching  fluid,  which  consists  in  confining  the 
mass  of  ore  in  a  vessel  with  a  body  of  leaching  fluid  of  lesser  specific  gravity  super- 
imposed upon  it,  carrying  portions  of  the  ore  upward  in  said  vessel  and  releasing 
it  above  the  body  of  leaching  fluid,  to  precipitate  it  through  said  body  and  simul- 
taneously convey  portions  of  the  leaching  fluid  below  the  surface  of  the  mass  of 
ore  and  releasing  it  and  permitting  it  to  rise  through  the  same. 

718099 — January  13,  1903.  S.  C.  C.  CURRIE.  Method  of  reducing  ores. — The 
step  in  the  art  of  treating  pulverized  ores  containing  precious  metals,  which  con- 
sists in  subjecting  the  ore,  in  a  closed  vessel,  to  the  action  of  hot  air  at  a  tempera- 
ture which  reduces  some  of  the  salts  in  the  ore  from  an  insoluble  to  a  soluble 
condition  in  water, ,  then  washing  ^  away  the  soluble  salts  with  water  and  then 
repeating  the  step  with  air  at  a  higher  temperature. 

719132— January  27,  1903.  W.  PAYNE,  J.  H.  GILLIES,  and  A.  GONDOLF. 
Process  of  treating  copper^  ores. — The  process  of  treating  copper  ores,  consisting 
in  first  roasting  to  an  oxide,  next  saturating  the  same  with  a  solution  of  ferrous 
sulphate  or  sulphate  and  chloride,  next  roasting  again  and  meanwhile  adding  a 
small  percentage  of  iron  sulphide  or  sulphur,  according  to  the  percentage  of  cop- 
per present,  and  finally  leaching  the  hqt  ore. 

719757 — February  3,   1903.     S.   C.   C.   CURRIE.     Process  of  treating  ores  con- 
Jy        taining  precious  metals. — The  method  of  treating  ore,  which  consists    in    heating 
the  raw  pulverized  ore  in  contact  with  steam,  and  plunging  the  heated  ore  into 
an  aqueous  alkaline  solution. 

723787 — March  24,  1903.  S.  TRIVICK.  Process  of  extracting  metals  from  ores. — 
A  process  for  evolving  nascent  chlorine  and  effecting  the  chlorination  of  metallic 
substances  in  order  that  they  may  be  extracted  from  a  metalliferous  mass  by 
rendering  them  solvent,  consisting  in  adding  to  the  mass  a  mixture  in  definite 
proportions  of  two  substances,  one  being  dry  chloride  of  lime  and  the  other  ferric 
sulphate,  the  proportions  being  such  as  to  result  in  the  formation  of  ferric  hypo- 
chlorite  and  ferric  chloride  which  will  evolve  nascent  chlorine. 

723949 — March  31,  1903.  G.  D.  VAN  ARSDALE.  Process  of  separating  copper 
from  ores. — The  process  of  extracting  copper  from  ores,  or  products  containing 
copper,  which  consists  in  separating  copper  from  cupric-sulphate  solutions,  with 
or  without  ferrous  or  other  suitable  sulphate,  and  of  simultaneously  producing 
free  sulphuric  acid,  by  adding  to  such  solutions  sulphur  dioxide  and  heating  with 
or  without  pressure,  whereby  copper  or  copper  compounds  are  thrown  down  in 
the  solid  form  to  be  subsequently  treated,  and  free  sulphuric  acid  is  formed,  and 
of  adding  the  acid  liquors  thus  obtained,  after  separation  from  the  copper  pre- 
cipitate, to  copper  ores,  whereby  the  copper  contained  in  them  is  dissolved  and 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  345 

the  original  solution  regenerated  and  the  process  repeated  and  thus  made  con- 
tinuous. 

724414 — March  31,  1903.  G.  H.  WATERBURY.  Copper  leaching  process. — The 
copper  leaching  process,  consisting  in  placing  the  suitably  pulverized  ore  in  a  leach- 
ing-tank,  adding  water,  acid,  common  salt,  and  oxide  of  manganese  in  suitable 
quantities,  heating  the  mass  by  the  introduction  of  steam  to  a  suitable  temperature, 
and  finally  subjecting  the  pulp  to  agitation  during  a  suitable  period. 

725257 — April  14,  1903.  T.  B.  JOSEPH.  Gold  extraction  process. — The  process 
of  extracting  precious  metals  from  ore  containing  the  same,  when  in  a  suitable 
condition,  which  consists  in  subjecting  the  said  ore  to  a  leaching  action  of  a  solu- 
tion  of  water,  cyanide  of  potassium,  hydrate  of  calcium,  carbon  dioxide,  and  bio- 
mine,  and  subsequently  precipitating  the  precious  metals  from  the  solution. 

725548 — April  14,  1903.  H.  R.  ELLIS.  Process  of  extracting  copper  from  car- 
bonate and  oxide  ores. — The  process  of  extracting  and  recovering  copper  from  its 
carbonate  or  oxide  ores  or  from  material  carrying  carbonates  or  oxides  of  copper,, 
which  consists  in  subjecting  the  ore  or  other  material  in  a  crushed  or  powdered 
state  to  the  action  of  a  carbonate  of  soda  or  its  described  equivalents  until  the 
copper  is  dissolved  and  subsequently  subjecting  the  charged  solution  to  electrolytic 
action. 

726802— April  28,  1903.  B.  T.  NICHOLS.  Ore-treating  process. — The  process 
for  treating  ore  preparatory  to  leaching,  consisting  first  in  mixing  the  suitably 
pulverized  ore  with  lime;  second,  applying  water  to  the  mixture  and  introducing 
steam  whereby  the  pulp  is  agitated  and  kept  at  a  suitable  temperature  until  cer- 
tain  impurities  which  retard  leaching  are  freed;  third,  washing  the  pulp  by  the 
introduction  of  water  and  continued  agitation;  fourth,  draining  on  the  water 
as  far  as  practicable;  and,  finally,  drying  the  ore. 

729760 — June  2,  1903.  G.  V.  GUSMAN.  Process  of  reducing  and  separating 
silver. — The  process  of  extracting  and  separating  silver  from  its  ores,  which  con- 
sists in  subjecting  roasted  ores  to  the  action  of  a  preprovided  aqueous  solution 
of  cupric  chloride  and  cuprous  chloride,  passing  the  resulting  solution  through 
granulated  metal,  and  removing  and  collecting  the  metallic  silver  from  said  metal. 

729819 — June  2,  1903.  J.  F.  WEBB.  Apparatus  for  use  in  extracting  metals 
from  ores. — A  tank  for  use  in  extracting  metals  by  chemical  process  from  their 
ores,  having  a  filter  bottom  and  means  for  discharging  air  within  the  tank  and 
downwardly  upon  the  said  bottom,  whereby  the  said  bottom  is  kept  free  frcm 
clogging  and  air  is  supplied  to  agitate  the  mass  within  the  tank  and  supply  oxygen 
thereto. 

734683 — July  28, 1903.  J.  F.  DUKE.  Process  of  obtaining  gold  from  sea-water.— 
The  process  of  obtaining  gold  from  sea-water  containing  the  same,  which  con- 
sists  in  precipitating  the  gold  by  carbonate  of  calcium. 

735098 — August  4,  1903.  C.  HOEPFNER.  Process  of  obtaining  lead  or  other 
metals  from  ores  or  mattes. — The  process,  which  consists  in  leaching  compounds 
containing  lead  and  iron  with  a  solution  of  cupric  chloride  containing  a  solvent 
of  the  chlorides  of  said  metals,  supplying  oxygen  to  produce  oxychloride  of  cop- 
per whereby  the  iron  is  precipitated,  and  precipitating  the  lead  as  a  sulphite  by 
means  of  a  sulphite  of  zinc. 

735512 — August  4,  1903.  H.  HIRSCHING.  Treatment  of  ores  containing  goldr 
silver,  copper,  nickel,  and  zinc. — The  process  for  extracting  gold,  silver,  copper, 
nickel,  and  zinc  from  substances  containing  the  same,  which  consists  in  subject- 
ing said  substances  to  the  action  of  an  acid,  washing  with  water  the  substance 
thus  treated,  thereby  forming  solutions  containing  compounds  of  gold  and  base 
metals,  and  then  subjecting  said  solutions  to  the  action  of  ammonia  for  the  pur- 
pose of  precipitating  the  gold  and  recovering  the  base  metals  from  the  solution, 
separately,  and  also  the  ammonia. 

739011 — September  15,  1903.  F.  LAIST.  Process  of  treating  ores. — The  method 
of  generating  hydrogen  sulphide  and  precipitating  copper,  which  consists  in  sub- 
j^cting  an  alkaline-earth  sulphide  in  presence  of  water  to  the  action  of  csrbcn 
d'ox'de,  thereby  generating  hydrogen  sulphide  and  precipitating  the  carbonate 
of  the  alkaline-earth  metal,  conducting  said  hydrogen  sulphide  into  the  presence 


346  APPENDIX. 

of  copper  in  solution,  thereby  precipitating  copper  sulphide  and  forming  a  sol- 
vent liquid,  treating  copper  ores  with  said  solvent  liquid,  and  collecting  said 
alkaline-earth  carbonate  and  reconverting  it  into  sulphide. 

740014 — September  29, 1903.  J.  HERMAN.  Process  of  treating  ores. — A  process 
of  extracting  copper  from  ores,  which  consists  in  treating  ore  containing  iron  to 
produce  ferrous  chloride,  utilizing  the  chloride  and  free  acid  to  dissolve  carbon- 
ates and  oxides  of  copper,  the  free  acid  being  adapted  to  neutralize  interfering  sub- 
stances and  to  attack  the  surface  of  the  particles  of  copper  oxide  or  carbonate, 
•and  regenerating  the  free  acid  by  the  electrolytic  precipitation  of  copper. 

740372 — September  29,  1903.  C.  ROGERS.  Process  of  extracting  zinc  from  sul- 
phide ores,  etc.— The  process  for  the  extraction  and  recovery  of  zinc  from  zinc 
containing  sulphide  ores  or  tailings,  which  consists  in  subjecting  the  same  to  a 
partial  sulphatizing  roast,  discharging  the  same  while  hot  into  water,  leaching 
the  same  with  said  water  and  with  dilute  sulphuric  acid,  subjecting  the  leached 
ores  or  tailings  to  a  second  sulphatizing  roast,  releaching  the  same  with  the  lix- 
ivium from  the  former  leaching,  and  repeating  said  operations  until  sufficient  zinc 
and  sulphur  are  removed. 

740701 — October  6,  1903.  A.  M.  G.  SEBILLOT.  Treatment  of  sulphide  ores. — A 
process  for  treating  ores  containing  sulphur  consisting  of  sulphating  the  ore  in 
a  closed  vessel  by  the  action  of  sulphuric  acid  upon  the  metallic  sulphides  at  a 
temperature  above  its  boiling-point  and  simultaneously  recovering  the  sulphuric 
acid  used,  calcining  the  sulphated  ore  at  a  temperature  of  700°  Centigrade  to  dis- 
sociate the  sulphate  of  iron  to  prevent  dissolving  of  a  too  great  quantity  of  sul- 
phate of  iron  in  .the  lixiviating  liquors,  and  then  lixiviating  the  calcined  ore. 

748662 — January  5,  1904.  A.  M.  G.  SEBILLOT.  Process  of  treating  copper 
ores. — The  process  for  extracting  pure  metals  from  mineral  ores,  consisting  in 
treating  the  ores  with  sulphuric  acid  at  the  evaporating-point  of  the  latter,  with- 
out roasting,  to  form  sulphates,  condensing  the  surplus  acid  fumes,  and  lixiviating 
the  sulphates  in  successively  deeper  baths  under  constant  agitation,  in  a  current 
flowing  in  direction  opposite  to  the  progress  of  the  ores. 

749700 — January  12,  1904.  P-  NAEF.  Process  of  lixiviating  ores. — The  method 
of  lixiviating  ores  or  other  pulverulent  materials,  which  consists  in  passing  the 
ore  downward  in  thinly  divided  layers  through  an  ascending  stream  of  leaching 
solution  and  at  the  same  time  passing  a  current  of  air  or  gas  repeatedly  through 
the  ore  layers  in  numerously  divided  jets,  whereby  the  ore  particles  are  agitated 
in  the  solution,  and  the  same  volume  of  gas  acts  successively  as  an  agitating  medium. 

752320 — February  16,  1904.  J.  B.  DE  ALZUGARAY.  Extraction  of  metals  from 
complex  ores. — In  the  treatment  of  complex  ores,  such,  for  instance,  as  contain 
copper,  lead,  silver,  and  zinc  in  comparatively  large  quantities,  the  process  of 
extracting  the  said  metals  selectively,  which  consists  in  leaching  the  ore  with  a 
solution  composed  of  a  mixture  of  a  chloride  of  an  alkali  or  earth-alkali  metal 
with  a  chloride  of  a  metal  other  than  those  of  the  alkali  or  earth-alkali  series  and 
an  acid  before  calcination  or  roasting  whereby  the  copper  is  obtained  in  solution 
then  washing  and  drying  the  ore,  roasting  the  partially  disintegrated  ore  at  a  low 
temperature,  extracting  the  metals  from  the  roasted  ore  in  form  of  salts  by  means 
of  a  second  and  weaker  leaching  solution  having  a  character  consonant  with  the 
nature  of  the  salt  it  is  desired  to  obtain,  and  recovering  the  metals  in  the  usual 
way. 

754643 — March  15,  1904-  K.  DANZIGER.  Process  of  separating  iron  pyrites 
from  zinc-blende. — A  process  for  separating  iron  pyrite  from  zinc-blende,  which 
consists  in  exposing  the  zinc-blende  to  the  action  of  air  moisture  and  heat,  and 
extracting  the  ferrous  salt  which  has  been  formed  by  the  oxidizing  action  by  water. 

755871 — March  29,  1904.  T.  A.  HELM.  Apparatus  for  treating  ore. — An 
apparatus  for  treating  pulverized  auriferous  ores,  comprising  a  rotatable  cylin- 
drical tank,  radially  depending  blades  in  the  tank  extending  the  length  thereof, 
a  circular  brace-frame  disposed  between  the  inner  ends  of  the  radial  blades,  as 
an  air  pipe  leading  into  the  tank,  faucets  to  draw  off  a  liquid  from  the  tank,  and 
means  to  rotate  the  tank. 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  347 

CLASS  75.— METALLURGY. 
SUBCLASS  86. — SOLUTION  AND  PRECIPITATION — APPARATUS. 

108158 — October  11,  1870.  W.  S.  LAIGHTON.  Improvement  in  apparatus  for 
precipitating  gold  and  silver  from  solutions. — The  invention  consists  in  combining 
two  vessels — one  to  receive  the  solution  to  be  precipitated  and  the  other  the  pre- 
cipitant— and  connecting  them  by  an  automatic  apparatus  that  shall  deliver  a 
certain  quantity  of  the  precipitant  into  the  other  vessel  every  time  it  is  filled  and 
provide  for  the  discharging  of  the  same,  the  quantity  of  the  solution  that  receives 
the  precipitant,  measured  out,  being  governed  by  a  hydrometer  or  hydrometric 
float,  which  is  used  to  operate  the  apparatus. 

213382 — March  18,  1879.  C.  C.  BITNER.  Improvement  in  apparatus  for  obtain- 
ing metallic  copper  from  its  solution. — The  invention  relates  to  a  novel  apparatus 
for  obtaining  metallic  copper  from  its  solution;  and  it  consists  in  the  employ- 
ment of  a  tank  or  vat  having  a  horizontal  perforated  diaphragm,  upon  which  is 
placed  a  quantity  of  iron.  This  tank  is  filled  with  a  solution  of  copper,  previously 
prepared  from  the  roasted  ore  in  the  usual  manner.  Through  the  top  of  this 
tank  a  steam  pipe  passes  and  extends  below  the  diaphragm,  so  that  the  solution 
is  heated  by  this  injected  steam,  and,  by  the  motion  which  its  action  gives,  the 
deposition  of  the  copper  is  hastened.  By  means  of  peculiarly  arranged  slides 
the  steam  is  admitted  above  the  diaphragm  through  holes  in  the  steam  pipe  to 
assist  the  process,  if  desired. 

234073— November  2,  1880.  R.  SCHULDER  and  E.  H.  RUSSELL.  Ore-leacher. — 
The  invention  consists  of  a  circular  frame  supporting  the  filter  and  moving  on  a 
circular  track  above  an  inclined  circular  table;  and  it  consists,  further,  of  three 
stationary  rollers,  designed  to  elevate  and  depress  the  filter  at  certain  points  as 
it  revolves,  of  a  device  for  feeding  the  substance  to  be  leached  upon  the  filter,  of 
a  device  for  applying  the  leaching  solvent,  and  of  a  precipitating  tank  to  contain 
the  solution  passing  through  the  filter. 

248768 — October  25,  1881.  J.  F.  N.  MACAY.  Filter. — The  invention  relates  to 
improved  apparatus  for  use  in  effecting  the  operations  of  dissolving  solids  in  liquids 
and  producing  chemical  reactions,  and  of  filtering  or  separating  liquids  from  solids 
in  chemical  and  metallurgical  processes,  in  which  a  soluble  substance  or  substances, 
mixed  or  combined  with  an  insoluble  substance  or  substances,  is  or  are  to  be  dis- 
solved separately  or  together,  wholly  or  partially,  in  a  given  solvent  or  solvents, 
and  the  solution  separated  by  filtration  from  the  undissolved  residue. 

In  effecting  the  separation  of  liquid  from  solid  matters  by  filtration  it  is  of 
importance  to  keep  the  filtering  surface  from  being  clogged  by  the  particles  of 
solid  matter,  and  to  present  a  clear  and  unobstructed  filtering  surface  for  effecting 
the  rapid  separtaion  of  the  liquid  from  the  solid  matters.  In  the  apparatus  of 
the  invention  this  important  condition  is  realized  in  a  very  effective  manner,  the 
construction  and  operation  of  the  apparatus  being  as  follows: 

Within  a  cylinder  of  wood  or  other  material  not  chemically  acted  on  by  the 
materials  treated  or  the  reagents  employed  is  inclosed  an  inner  cylinder  of  hard 
wood,  or  of  hard  earthenware  or  stoneware  or  other  material  not  chemically  acted 
on  by  the  materials  treated  or  the  reagents  employed,  this  inner  cylinder  being 
perforated  with  holes  and  lined  internally  or  externally,  but  preferably  inter- 
nally, with  asbestos  cloth  or  other  suitable  filtering  material. 

Between  the  inner  and  outer  cylinder  there  is  an  annular  space,  and  the  inner 
cylinder  is  kept  in  place  by  longitudinal  and  circumferential  partitions,  the  former 
of  which  divide  ftie  annular  space  into  a  number  of  distinct  compartments  each 
provided  with  a  draw-off  cock  for  running  off  the  liquid  when  separated  by  fil- 
tration. This  cylinder  is  capable  of  being  rotated,  and  is  provided  with  doors 
or  manholes  in  one  of  the  heads  by  which  the  matters  to  be  treated  may  be  intro- 
duced and  the  undissolved  residue  removed;  and  the  cylinder  is  also  provided 
with  a  tubular  journal  or  journals  for  the  introduction  of  steam,  water,  air,  or 
other  liquids  or  gases,  under  pressure  or  otherwise,  which  may  be  blown,  forced, 
or  drawn  into  the  annular  space  for  the  purpose  of  keeping  the  filtering  surface 


348  APPENDIX. 

clear  and  of  acting  chemically  or  mechanically  upon  the  contents  of  the  cylinder. 
I  place  within  the  inner  cylinder  the  ore  or  other  matter  to  be  treated  (previously 
ground  or  otherwise  reduced  to  a  pulverulent  state),  together  with  the  reagents 
.or  solvents  by  which  it  is  to  be  treated.  By  imparting  rotary  motion  to  the  cylinder 
'(the  draw-off  cocks  and  manholes  being  closed)  the  solid  matters  are  brought 
into  intimate  contact  with  the  solvents  or  reagents,  and  by  forcing  steam,  water, 
air,  or  other  liquids  or  gases  into  the  space  between  the  ini  ^r  and  outer  cylinders, 
and  thence  through  the  filtering  medium  into  the  inner  cylinder,  any  solid  mat- 
ters that  may  adhere  to  the  filtering  surface  are  disengaged  therefrom,  whereby 
the  said  surface  is  kept  clear,  the  solid  matters  are  kept  in  suspension  in  the  liquid, 
and  chemical  action,  which  the  liquid  or  gaseous  reagents  may  be  capable  of  exert- 
ing on  the  said  matters,  takes  place  under  the  most  favorable  circumstances  as 
regards  the  intimate  mixture  of  the  reagents  with  the  matters  and  the  large  sur- 
faces exposed  to  their  action.  The  annular  space  between  the  inner  and  outer 
cylinders  being  divided  into  compartments  by  longitudinal  divisions,  the  liquid 
which  passes  through  into  it  is  carried  round  by  the  rotation  of  the  cylinder  and 
flows  back  into  the  inner  cylinder,  thus  helping  to  keep  the  filtering  surface  clear 
and  unobstructed.  When  the  soluble  substances  are  dissolved  or  chemically 
acted  upon,  and  it  is  desired  to  separate  the  liquid  from  the  solid  matters,  the 
draw-off  cocks  are  opened,  and  then,  by  giving  a  slow  rotary  motion  to  the  appara- 
tus, the  liquid  may  be  decanted  off  from  the  bulk  of  the  solid  matter  and  at  the 
same  time  filtered  from  any  such  matters  which  it  may  hold  in  suspension  by  passing 
through  the  filtering  medium.  By  this  rotary  decanting  action  a  practically  clear 
filtering  surface,  unobstructed  by  solid  matter,  is  constantly  presented  for  the 
liquid  to  pass  through. 

251718 — January  3,  1882.  A.  E.  JONES.  Apparatus  for  separating  gold  from 
quartz  and  rock  tailings. — The  invention  consists  in  the  arrangement  and  applica- 
tion of  a  suitable  fibrous  material  in  combination  with  machinery,  so  that  the 
fibrous  material  will  unite  or  collect  to  itself  the  gold  and  carry  and  deposit  the 
same  to  a  place  designated,  where  it  may  be  collected  and  treated  as  desired  in 
separating  the  precious  metal  from  its  sand  and  ore.  Any  fibrous  matter  that 
will  form  a  pulp  when  mixed  with  water  is  used  to  coat  a  wire-cloth  screen  as  in 
paper-making,  and  then  entangle  the  fine  gold  in  suspension  in  the  water. 

301460 — July  1,  1884.  J-  L.  RUSSELL.  Slime  filter. — The  invention  consists 
of  a  trough'  containing  at  intervals  within  it  a  series  of  double  filtering  boxes 
covered  with  wire  gauze  and  filled  with  charcoal,  sponge,  or  any  known  filtering 
substance,  and  the  claims  cover  the  trough  poised  over  filter  sections  provided 
with  adjustable  partitions,  as  well  as  the  combination  of  a  sand  box,  a  sluice  pro- 
vided with  adjustable  partitions,  filters  composed  of  frames  and  wire  gauzes,  and 
gutters. 

325835 — September  8,  1885.  H.  C.  and  J.  A.  HENDERSON.  Apparatus  for  con- 
centrating ores. — The  apparatus  for  concentrating  ores,  consisting  of  an  outer 
tank,  an  inner  tank  provided  with  fabric  ends,  and  a  perforated  feed-box  hav- 
ing its  lower  end  below  the  top  edge  of  the  tank,  a  space  being  left  between  the 
sides,  ends,  and  bottom  of  the  tanks  whereby,  when  the  water  is  received  by  the 
perforated  feed-box,  it  will  pass  into  the  inner  tank  and  slowly  filter  through 
the  fabric  ends  thereof  and  flow  over  the  top  edge  of  the  outer  tank,  the  fabric 
ends  preventing  the  formation  of  a  current  and  causing  the  particles  of  ore  to  be 
precipitated. 

366103 — July  5, 1887.  O.  HOFMANN.  Process  of  extracting  silver  from  its  ores  by 
lixiviation. — The  invention  relates  to  a  certain  improvement  in  the  lixiviation  process 
by  which  the  ore,  after  having  been  subjected  to  a  chloridizing  roasting,  is  in- 
troduced in  a  series  of  troughs,  first,  together  with  water  to  dissolve  the  base- 
metal  chlorides,  and,  sceond,  together  with  the  solution  used  in  the  ordinary 
lixiviation  process  to  dissolve  the  silver.  The  ore  and  water  are  introduced  either 
by  means  of  a  mixing-box  or  an  agitator,  and  are  allowed  to  flow  in  these  troughs 
for  some  distance,  and  finally  conveyed  by  them  into  settling-tanks.  The  water 
while  running  in  the  troughs  dissolves  the  base-metal  chlorides.  In  the  settling- 
tanks  the  ore  separates  quickly  from  the  liquid.  The  latter  is  drawn  off  and  con- 
veyed to  other  tanks  for  the  usual  treatment.  The  ore  sediment  containing  the 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  349 

silver  is  now  sluiced  or  charged  again  in  a  similar  series  of  troughs  with  a  solution 
which  has  the  property  of  dissolving  chloride  of  silver,  like  hyposulphite  of  lime 
or  soda,  concentrated  salt  solution,  Russell's  "extra  solution"  (a  compound  of 
hyposulphite  of  lime  or  soda  and  bluestone),  etc.  By  passing  through  this  second 
series  of  troughs  the  silver  chloride  dissolves.  Ore  and  solution  run  into  tanks 
which  are  provided  with  filter  bottoms  and  allowed  to  separate.  The  tailings 
settle  to  the  bottom,  while  the  clear  solution,  now  containing  the  silver,  is  drawn 
off  and  conveyed  into  the  precipitation-tanks  for  the  usual  treatment. 

370871 — October  4,  1887.  F.  F.  HUNT.  Apparatus  for  agitating  solutions  in 
the  leaching  of  metals  from  their  ores. — The  invention  relates  to  an  improvement  in 
apparatus  for  agitating  the  acid  solutions  formed  in  the  leaching  of  copper  and 
other  ores;  and  the  object  of  the  same  is  to  provide  a  form  of  rotary  agitator  in 
which  the  heavier  portions  of  the  charge  cannot  accumulate  at  the  centre  of  the 
apparatus  and  escape  the  action  of  the  agitating  arms,  which  will  also  produce  a 
more  perfect  agitation  of  the  solutions  than  has  heretofore  been  possible,  and  which 
will  be  more  durable  and  economical  to  construct  than  the  forms  in  present  use. 

Heretofore  the  agitators  used  in  leaching  works  have  usually  been  made  with 
flat  bottoms  and  have  been  provided  with  stirring  or  agitating  arms  of  conical 
shape  at  the  base,  arranged  to  rotate  a  slight  distance  above  the  bottom.  In 
the  invention  this  arrangement  is  reversed,  and  the  agitating  tank  is  constructed 
with  a  cone  of  small  altitude  placed  apex  upward  in  the  centre  of  the  bottom  and 
covering  a  considerable  portion  thereof,  and  is  provided  with  agitators,  the  arms 
of  which  are  provided  with  concave  shoes  and  are  arranged  to  rotate  in  close  prox- 
imity to  the  cone  in  the  bottom  of  the  tank. 

^1 26 '10 — October  8,  1889.  J.  B.  HANNAY.  Apparatus  for  applying  chlorine  to 
the  extraction  of  gold  from  ores. — This  invention  relates  to  means  of  extracting  from 
ores  precious  metals,  especially  gold,  in  the  form  of  chloride  solution.  For  this 
purpose  an  apparatus  is  employed  which  consists  of  a  chlorinating  vessel,  a  set 
of  circulating  pumps,  a  filter-press,  and  a  chlorine  pump,  or  sets  of  these,  with 
suitable  communicating  pipes,  cocks,  and  valves  for  operating  in  the  following 
manner:  Having  reduced  the  ore  to  a  fine  powder,  it  is  mixed  with  water  or  with 
chlorinated  water  to  a  condition  of  thin  sludge,  which  can  be  pumped.  Then  charge 
the  chlorinating  vessel  with  this  sludge  and  apply  the  pumps  to  cause  its  circula- 
tion therein,  drawing  from  the  upper  part  and  discharging  into  the  lower  part, 
while  chlorine  gas  is  pumped  into  the  vessel,  preferably  to  a  pressure  considerably 
above  that  of  the  atmosphere.  After  circulation  has  gone  on  for  some  time,  until 
the  metal  in  the  ore  is  mostly  dissolved  by  the  chlorine,  the  sludge  is  pumped  by 
the  circulating  pumps  into  the  filter-press,  additional  pressure  being  given,  if  re- 
quired, by  using  the  chlorine  pump  to  force  air  into  the  upper  part  of  the  chlorin- 
ating vessel.  The  liquid  issuing  from  the  filter-press  containing  in  solution  the 
metallic  chloride  is  treated  in  any  of  the  known  ways  for  separating  the  metal 
and  recovering  the  chlorine.  In  some  cases  the  solution  discharged  from  the  filter- 
press  may  be  used  in  a  subsequent  operation  to  form  the  sludge  by  its  admixture 
with  a  fresh  quantity  of  pulverized  ore,  and  this  may  be  done  repeatedly,  so  as  to 
obtain  finally  a  filtered  liquor  rich  in  chloride. 

As  it  is  advantageous  to  charge  the  chlorinating  vessel  with  an  excess  of  chlorine 
above  that  which  enters  into  combination  with  the  metals,  the  inventor  prefers 
to  collect  such  excess  before  discharging  the  sludge  by  blowing  in  a  little  steam 
to  warm  the  sludge  and  allowing  the  free  chlorine  thus  liberated  to  pass  either 
into  a  gasometer  or  into  another  chlorinating  vessel;  or  an  exhaust-pump  may  be 
employed  to  draw  off  the  free  chlorine. 

When  metals  such  as  silver  are  present,  having  insoluble  chlorides,  the  blocks 
which  are  taken  from  the  filter-press,  and  which  contain  these  chlorides,  may  be 
reduced  to  sludge,  as  before  mentioned,  and  may  be  subjected  to  the  same  treat- 
ment with  a  suitable  solvent  instead  of  the  chlorine. 

418138— -December  24,  1889.  J.  S.  MACARTHUR.  Metallurgical  filter— K  metal- 
lurgical filtering  apparatus  for  separating  a  precious  metal  from  a  solution  containing 
said  metals,  consisting  of  a  series  of  vessels,  each  of  which  has  an  inlet  tube  near 
its  bottom,  an  outlet  tube  near  its  top,  and  a  perforated  false  bottom  above  th3 
inlet  tube,  zinc  sponges  disposed  in  the  several  vessels,  pipes  connecting  the  inlet 


350  APPENDIX 

and  outlet  tubes  of  the  several  vessels,  and  a  reservoir  for  supplying  the  solution 
to  the  first  vessel  of  the  series. 

425025 — April  8,  1890.  D.  DENNES  and  T.  K  ROSE.  Apparatus  for  leaching 
ores. — In  a  leaching  apparatus,  a  movable  table,  having  a  flange  or  wall  projecting 
from  its  upper  surface  to  form  a  receptacle  for  filtering  material,  the  said  receptacle 
being  of, less  diameter  than  the  upper  surface  of  the  table,  whereby  a  packing 
receiving  ledge  projects  beyond  the  base  of  the  said  wall  or  flange,  combined  with 
the  leaching  cylinder,  the  lower  end  of  which  is  constructed  to  receive  said  wall 
or  flange,  while  the  ledge  abuts  against  said  lower  end  of  the  cylinder. 

442262 — December  9,  1890.  S.  TRIVICK.  Apparatus  for  treating  ores  to  obtain 
precious  metals  therefrom. — This  invention  relates  to  improvements  in  apparatus 
forming  a  plant  for  treating  roasted  ground  ores  to  obtain  precious  metals  there- 
from, adapted  for  use  in  treating  roasted  ground  ores  of  precious  metals  that  have 
been  roasted  by  any  known  or  suitable  method. 

The  apparatus  consists,  essentially,  of  a  vessel  (preferably  employing  a  pair 
at  least  of  such  vessels,  so  as  to  change  from  one  to  the  other  of  the  pair  in  working) 
having  a  porous  bottom  on  which  the  ground-roasted  ores  rest;  means  of  supply 
of  leaching  liquid  controlled  by  valve;  means  of  drawing  off  leached  liquid,  con- 
veyance thereof  to,  and  means  of  stirring  said  liquid  in  a  mixing  chamber — a  filter 
vessel  having  a  porous  floor — and  means  of  pumping  the  filtered  liquid  to  a  reser- 
voir; means  of  evaporating  the  leaching  liquor  to  recover  the  contained  salts; 
also  recovering  the  copper  salts  for  reuse,  and  means  of  heating  the  leaching  liquid, 
and  also  means  of  desiccating  the  product. 

The  invention  also  consists  in  a  furnace  for  roasting  ores  of  precious  metals, 
comprising,  among  other  features,  a  chamber,  coils  of  piping,  a  tank,  reservoir, 
a  force-pump,  a  system  of  heating  pipes,  leaching  reservoir,  tanks  with  porous 
floors,  and  a  mixing  vessel  with  rotating  stirrers  therein. 

449813 — April  7,  1891.  J.  CRAGG.  Apparatus  for  extracting  gold  or  silver  from 
ares. — In  an  apparatus  for  extracting  gold  or  other  metals  from  their  ores  in  solu- 
tion, a  tower  and  a  mixer,  which  consists  of  a  trough  having  pipes  to  conduct  the 
reagents  in  liquid  solution,  which  enter  the  same  from  different  sides  and  terminate 
out  of  alignment  about  centrally  of  the  trough,  combined  with  a  hopper  placed  over 
the  ends  of  the  said  pipes  and  an  overflow  plate  leading  to  the  said  tower. 

456323— July  21,  1891.  P.  L.  GIBBS.  Ore-leaching  machine. — This  invention 
has  reference  to  ore-leaching  machines  in  which  a  rotating  annular  series  of 
ore  receptacles  pass  successively  under  an  ore  vat  containing  the  crushed  ore  in 
a  solution  to  receive  their  respective  contents  or  to  be  otherwise  filled,  and  to 
discharge  the  filtrate  during  their  transit  into  a  suitably  placed  discharging  con- 
duit or  launder  and  at  a  predetermined  point  in  their  orbital  movement  and  auto- 
matically discharge  the  residuum. 

The  objects  of  this  improvement  are,  first,  to  provide  a  suitably  suspended 
vat  to  receive  the  ore  in  a  solution,  or  dry  or  roasted  ore,  and  adapted  by  suitable 
openings  in  the  bottom  thereof  to  optionally  discharge  said  contents;  second, 
to  provide  a  series  of  leaching-vats  to  pass  successively  under  said  primary  vat 
and  respectively  receive  from  the  latter  a  proper  quantity  of  its  contents;  third, 
to  provide  suitable  mechanism  for  supporting  and  progressing  said  secondary  vats; 
fourth,  to  provide  a  conduit  or  launder  to  receive  and  carry  off  the  filtrate  from 
said  leaching  or  secondary  vats;  and,  fifth,  to  afford  facilities  to  automatically 
discharge  the  residuum  from  said  leaching-vats  preparatory  to  their  refilling. 

463120 — November  10,  1891.  D.  DENNES.  Leaching-vat  for  separating  precious 
metals  from  their  ores. — An  ore-leaching  apparatus  consisting  of  a  closed  vat  or 
separating  vessel  having  a  removable  bottom  carrying  a  filter-bed  in  its  upper 
portion  and  an  auxiliary  chamber  beneath,  provided  with  a  removable  bottom  and 
a  filter-bed,  and  a  suitable  pipe  connection  between  the  separating  vessel  and 
said  auxiliary  chamber  in  its  bottom. 

464672— -December  8,  1891.  W.  D.  BOHM.  Apparatus  for  separating  gold 
and  silver  from  ore. — The  inventor  places  the  powdered  or  divided  ore,  or  material 
to  be  treated  for  the  obtainment  of  the  gold  or  silver,  or  both,  in  a  vessel  or  vat, 
or  vessels  or  vats,  and  through  it  passes  the  leaching  solution,  preferably  pre- 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  351 

viously  heated.  By  means  of  a  force-pump,  the  leaching  solution  is  forced  up 
through  the  ore  and  through  a  filter  at  the  top.  The  solution  and  the  precious 
metal  which  it  now  contains  pass  into  a  vessel  in  which  it  is  agitated  with  a  pre- 
cipitating agent.  From  this  last-named  vessel  the  solution  is  forced  up  by  a  force- 
pump  through  a  vessel  having  a  filtering  arrangement,  such  as  a  porous  diaphragm, 
at  the  top,  so  that  the  solid  matter  is  retained  thereby,  the  liquid  passing  off  to 
be  heated  again  and  to  be  restrengthened  by  the  addition  of  the  necessary  further 
quantity  of  leaching  chemicals  and  passed  back  to  the  leaching  vat  or  vats  for 
reuse.  The  pressure  under  which  the  liquids  are  forced  up  through  the  leaching- 
vat  and  precipitant  vessel  should  be  at  least  eighteen  pounds  per  square  inch. 
At  intervals  the  solid  matter  retained  by  the  last-named  filter  vessel  is  passed  into 
a  filter-press  or  equivalent  apparatus,  whereby  it  is  deprived  of  the  greater  part  of 
its  moisture.  The  ore  which  has  been  leached  is  then  drained  of  all  solution  and 
washed  free  from  the  last  traces  thereof  with  water,  preferably  hot,  and  then  can 
be  washed  out  of  the  vat  or  vats  with  acidulated  water,  and  passed  over  zinc  or 
alloy  of  zinc  with  other  suitable  metal,  so  that  hydrogen  is  evolved,  which  reduces 
any  precious  metal  still  remaining  in  the  ore  to  the  metallic  state,  or  such  state 
that  it  is  taken  up  when  the  ore  is  afterwards  passed  over  mercury — for  instance, 
over  amalgamated  copper. 

495385 — April  11,  1893.     F.  WEBB.     Method  of  and  apparatus  for  extracting 
precious  metals  from  their  ores. — The  inventor  claims,  in  means  for  extracting  pre- 
cious metals  from  their  ores,  the  combination  of  an  outer  vessel  resting  in  suit- 
able trunnions  for  containing  the  reagent  or  chemical  solution,  and  having  inlet 
and  outlet  pipes  communicating,  respectively,  with  the  top  and  bottom    thereof 
through  said  trunnions,  a  perforated  vessel  in  said  outer  chamber,  and  adapted  to 
receive  the  crushed  ore,  and  provided  with  a  manhole  opening  extending  to  the      \> 
outside  of  the  latter,  and  means  for  reciprocating  the  inner  vessel  and  for  rotating       / 
the  outer  vessel  on  its  trunnions,  whereby  the  contents  of  the  inner  vessel  may  be  tf 
discharged.     Also,  the  method  of  separating  precious  metals  from  their  ores,  con-  | 
sisting  in  placing  the   disintegrated  or  crushed  ore  in  a  closed   perforated   vessel  I 
and  causing  the  latter  to  reciprocate  in  the  reagent  or  chemical  solution,  whereby  ' 
the  latter  is  enabled  to  more  effectually  act  upon  the  ore. 

497856 — May  23,  1983.     C.  G.  BROWN.     Ore-tank. — In  a  tank  for  leaching  or 
saturating  ore,  the  combination  with  a  false  bottom  and  a  piece  of  textile  material 
laid  upon  the  upper  side  of  said  false  bottom;   of  a  series  of  vertically  disposed       ^ 
perforated  tubes  designed  and  adapted  to  hold  the  pieces  of  ore  apart  and  pro- 
mote the  circulation  of  the  leaching  or  saturating  solution. 

525970— September  11,  189 4.  J.  STOKER  and  B.  T.  LACY.  Method  of  and  appa- 
ratus for  dissolving,  leaching,  and  filtering. —  The  inventor  claims  the  improved 
method  of  dissolving,  leaching,  and  filtering,  consisting,  essentially,  in  connecting 
a  plurality  of  closed  tanks  in  series,  then  introducing  an  expansible  medium  upon 
a  body  of  non-compressible  fluid  contained  in  a  terminal  tank  to  force  the  said 
fluid  under  pressure  into  the  successive  tanks  and  through  the  material  under 
treatment  until  it  reaches  the  final  tank,  then  connecting  this  last-named  tank 
with  the  initial  tank,  and  finally  introducing  pressure  in  the  said  final  tank  to  v 
force  the  fluid  therefrom  so  that  it  may  be  returned  to  said  initial  tank.  And  in  an  2 
apparatus  for  dissolving,  leaching,  and  filtering,  the  combination  of  the  tank 
adapted  to  contain  the  material  to  be  treated,  a  tank  adapted  to  contain  a  non- 
compressible  fluid  and  connected  with  a  source  of  steam,  gas,  or  vapor  supply,  a 
valve-controlled  pipe  from  said  fluid  tank  to  said  material-containing  tank,  a  final 
tank  beyond  the  material-containing  tank,  a  valve-controlled  pipe  connecting  said 
material -containing  tank  with  said  final  tank,  whereby  the  fluid  is  forced  into  said 
final  tank,  a  valve-controlled  pipe  connecting  said  final  tank  with  the  initial  fluid 
tank,  and  means  for  admitting  an  expansive  medium  into  said  final  tank  to  force 
the  fluid  therefrom  back  into  the  initial  tank. 

530397 — December  4,  1894.  N.  H.  CONE.  Filter-barrel. — In  an  apparatus 
of  the  class  described,  the  combination  with  a  revolvable  cylinder  having  a  hollow 
trunnion,  and  a  head  provided  with  radiating  channels  having  independent  valves 
of  a  filter  arranged  in  said  cylinder  and  valves  for  opening  or  closing  said  channels 
independently  of  each  other. 


352  APPENDIX. 

536981— April  2,  1895.  T.  L.  WISWALL  and  J.  B.  FRANK.  Receptacle  for 
recovering  precious  metals  from  solutions. — This  invention  relates  to  apparatus 
wherein  the  recovery  of  the  precious  metals  from  cyanide  and  other  solutions  is 
effected  by  passing  thq  solutions  through  a  filtering  material,  by  which  the  precious 
metals  are  precipitated.  And  the  inventor  claims,  in  apparatus  for  the  extrac- 
tion of  precious  metals  from  solutions,  the  precipitating  box,  having  an  undulating, 
sinuous  passage  from  end  to  end,  comprising  a  series  of  alternate  angular  depres- 
sions and  elevations,  provided  with  a  series  of  retaining  pins,  attached  to  the  interior 
of  said  precipitating  -box,  and  extending  into  the  precipitating,  filtering  material 
within  said  passage. 

549177 — November  5,  1895.  T.  L.  WISWALL  and  J.  B.  FRANK.  Apparatus 
for  recovery  of  precious  metals  from  tJieir  solutions. — The  inventors  claim  in  appa- 
ratus for  the  recovery  of  precious  metals  from  their  solutions  a  precipitating  box 
adapted  to  contain  a  finely  subdivided,  metallic,  precipitating  reagent,  divided 
into  a  series  of  compartments  by  removable  perforated  partitions,  said  partitions 
being  provided  with  adjustable  gates,  controlling  the  flow  of  said  solution  through 
the  perforations  in  said  partitions  for  the  purposes  indicated. 

549622 — November  12,  1895.  P.  ARGALL.  Apparatus  for  extraction  of  precious 
metals. — The  specifications  set  forth  that  in  the  treatment  of  ores  by  the  cyanide 
process  to  extract  their  gold  and  silver  contents,  it  is  the  usual  practice  to  place 
the  ores  in  open  leaching-tanks  and  allow  the  cyanide  solution  to  percolate  through 
the  mass  and  so  dissolve  and  remove  the  precious  metals  in  solution.  This  method 
is  on  the  whole  fairly  efficient,  but  it  occupies  considerable  time  (forty  to  eighty 
hours)  and  causes  a  large  consumption  of  cyanide  through  decomposition,  owing 
to  its  long  contact  with  the  ore  and  atmosphere.  With  many  classes  of  ore,  how- 
ever, it  is  found  that  agitation  of  the  ore  and  solution  is  necessary  in  order  to  obtain 
the  best  results  or  largest  extraction  of  precious  metals.  Particularly  is  this  the 
case  with  silver-bearing  ores  or  ores  parrying  considerable  value  in  silver. 

The  agitators  heretofore  in  use  shorten  the  time  necessary  to  dissolve  the  precious 
metals;  but  they  invariably  cause  a  large  consumption  of  cyanide,  due  chiefly 
to  the  continuous  agitation  of  the  solution  in  open  tanks  or  in  partly  filled  barrels 
in  the  presence  of  an  excess  of  air,  while  the  ore  when  discharged  from  the  agita- 
tors is  in  such  a  condition  that  very  often  it  cannot  be  leached,  or  at  best  but 
part  of  the  cyanide  solution  containing  the  dissolved  gold  can  be  separated  from 
the  ores.  Then  again,  the  agitators  now  in  use  are  of  such  small  capacity  as  to 
add  largely  to  the  cost  of  treating  the  ores. 

This  invention  relates  to  a  new  machine  for  treating  ores  by  continuous  agita- 
tion and  continuous  percolation  under  pressure  or  by  means  of  vacuum  and  either 
with  or  without  external  or  additional  heat.  And  the  inventor  claims  a  perco- 
lator for  treating  ores  by  the  cyanide  process  comprising  an  outer  shell  capable 
of  being  closed,  air-tight,  hollow  trunnions  upon  which  said  vessel  rotates,  con- 
centric tubes  extending  axially  through  the  vessel,  the  outer  tube  being  covered 
by  a  filtering  medium,  a  passage  connecting  the  annular  space  between  the  tubes 
with  one  of  the  hollow  trunnions,  and  a  pipe  communicating  with  the  chamber 
surrounding  the  outer  tube.  The  invention  includes  other  features  of  a  minor 
or  subsidiary  character. 

552807 — January  7,  1896.  H.  G.  WILLIAMS.  Method  of  and  apparatus  for 
extracting  metals  from  their  ores. — In  an  apparatus  for  the  extraction  of  precious 
metals  from  their  ores  by  the  wet  process,  the  combination  of  one  or 
more  castings,  with  screw  conveyers  and  mixers,  means  for  feeding  the  solid 
and  liquid  matters  thereto,  and  a  dam  placed  at  the  discharge  end  of  the 
casing  for  each  conveyer,  having  its  surface  inclined  upon  the  side  next  to 
the  conveyer  flights  or  blades,  for  the  purpose  of  maintaining  the  admixture 
of  the  liquids  and  solids  by  preventing  the  liquid  from  traveling  faster  than  the 
solid  and  still  giving  passage  by  reason  of  its  incline  to  the  travel  of  the  solids  over 
the  same;  and,  in  the  extraction  of  precious  metals  from  their  ores  by  the  wet 
process,  the  method  of  continuously  and  uninterruptedly  precipitating  and  sepa- 
rating the  metals,  which  consists  in  simultaneously  introducing  the  precipitating 
agent. and  an  independent  agitating  blast  of  steam  into  the  solution  of  metal  in 


PATENTS  RELATING  TO  CYANIDE   PROCESSES.  353 

direction  as  described  to  secure  admixture  and  agitation  by  a  whirling  motion 
and  the  agglomeration  of  the  precipitated  particles  of  metal,  and  continuously 
separating  the  precipitate  by  settlement  and  filtration. 

567144 — September  8,  1896.  S.  B.  LADD.  Apparatus  far  leaching  ores. — The 
object  of  the  present  invention  is  to  provide  an  economical  and  practical  apparatus 
for  the  lixiviation  of  ores,  and  particularly  applicable  to  cases  where  a  large  mass 
of  material  has  to  undergo  treatment — as,  for  example,  in  the  lixiviation  of  low- 
grade  gold  ores  by  the  cyanide  process — and  where  the  expense  of  handling  mate- 
rial  becomes  an  important  factor  with  respect  to  the  commercial  working  of  the 
process.  The  invention  applies,  genetically,  to  the  lixiviation  of  comminuted 
or  pulverized  material  of  any  character,  but  it  is  especially  designed  for  the  lix- 
iviation of  ores  by  the  cyanide  process,  for  in  the  treatment  of  ore  pulp  or  slimes 
by  the  cyanide  and  other  like  processes  a  large  amount  of  material,  often  of  a  low 
grade,  has  to  be  subjected  to  the  action  of  an  aqueous  solution  of  a  cyanide  or 
other  solvent,  or  to  the  successive  action  of  a  series  of  solutions.  The  common 
course  of  procedure  in  working  the  cyanide  process  on  a  large  scale  is  to  run  the 
ore  pulp  into  large  vats  and  then  to  cause  the  proper  solutions  for  leaching  out 
the  precious  metals  to  percolate  therethrough,  for  example,  first  an  alkaline  solu- 
tion, when  the  ore  is  acid,  then  a  strong  solution,  then  a  weaker  solution,  and  finally 
water  to  wash  the  pulp.  The  vat  is  then  emptied  and  refilled  with  fresh  ore  pulp; 
also,  the  solvent  process  is  sometimes  worked  by  agitating  the  pulp  and  leaching 
solution  in  pans  or  vessels.  Both  systems  require  considerable  labor  and  are 
intermittent. 

Another  object  of  the  present  invention  is  to  provide  means  to  make  the  extrac- 
tion process  continuous,  so  that  the  ore  pulp  shall  progressively  and  continuously 
be  associated  with  the  solutions  or  the  washings  which  may  be  necessary  for  thor- 
oughly exhausting  the  values  from  the  ore.  This  is  accomplished  by  construct- 
ing a  leaching-tank,  in  the  form  of  a  long  trough,  which  may  be  divided  by  one 
or  more  fixed  or  removable  bridges  into  so  many  trough  sections  as  are  required 
for  the  several  solutions  or  washings  when  one  leaching  is  not  sufficient;  or  by 
providing  a  series  of  tanks  or  troughs  operatively  arranged  with  respect  to  each 
other,  employing  in  connection  therewith  a  conveyer  for  the  ore  pulp  adapted 
to  continuously  feed  the  pulp  with  a  steady  movement  through  the  several  solu- 
tions in  an  uninterrupted  flow  through  the  apparatus  to  the  point  of  discharge 
without  any  intermediate  stoppage  or  handling  of  the  same  whereby  the  lixivia- 
tion of  the  ore  is  effected. 

For  the  purpose  of  rendering  the  operation  continuous,  provision  is  made  for 
a  constant  drawing  off  of  the  charged  solution  or  solutions  from  the  leaching 
troughs  and  an  inflow  of  fresh  solution  thereto.  In  the  case  of  the  first  cyanide 
solution  the  inflow  is  preferably  at  the  ore-entrance  end  of  the  trough  or  trough 
section  and  the  current  is  with  the  ore,  thus  catching  the  fine  float  gold  carried 
by  the  fresh  pulp;  but  in  the  subsequent  troughs  or  trough  sections,  and  also 
in  the  first,  if  preferred,  the  inflow  of  the  solution,  (or  washing  water)  is  prefer- 
ably made  at  the  ore-exit  end  and  the  outflow  of  the  solution  is  at  the  opposite 
end  where  fresh  ore  or  pulp  is  entering  the  trough  or  trough  section.  Thus,  in 
this  latter  case,  the  flow  of  the  solution  is  opposite  to  that  of  the  ore.  The  fresh 
cyanide  solution  first  acts  upon  pulp  which  is  largely  leached  out,  and  as  the  solu- 
tion becomes  more  and  more  charged  with  the  gold  or  precious  metals  it  meets 
Eulp  that  is  progressively  richer  in  the  metals,  and  the  conditions  are  therefore 
ivorable  for  effecting  a  complete  extraction  of  the  precious  metals  by  the  sol- 
vent. As  a  preferred  form  of  conveyer,  slowly-moving  blades  transverse  to  the 
trough  or  tank  are  used.  These  blades  extend  across  the  tank  with  just  enough 
room  at  the  sides  for  clearance,  and  they  reach  from  above  the  surface  of  the  solu- 
tion down  to  and  into  the  ore  pulp  on  the  bottom  of  the  tank  with  openings  or 
notches  in  or  along  the  lower  part  of  the  blades  for  the  underflow  of  the  solution. 
These  blades  divide  the  trough  or  tank  into  a  number  of  communicating  divisions 
and  form  what  may  be  called  "traveling  partitions,"  moving  slowly  through  the 
trough  from  end  to  end  thereof.  The  lower  edges  of  these  blades  are  preferably 
fashioned  with  rake  teeth,  and  they  open  up  and  rake  along  the  layer  of  ore  pulp 
on  the  bottom  of  the  tank  and  effect  a  slow  and  progressive  movement  of  the  mass 


354    t  APPENDIX. 

with  a  constant  plowing  therethrough  and  exposure  of  fresh  portions  thereof  to 
the  action  of  the  solution,  while  the  solution  in  the  tank  as  the  series  of  blades 
move  forward  has  to  flow  back  through  the  notches  or  openings  in  the  bottom 
of  the  traveling  blades  from  each  of  these  divisions  formed  by  the  blades,  re- 
spectively, into  the  adjacent  rear  division,  and  thus  there  is  secured  a  constant 
and  steady  underflow  of  the  solution  in  close  proximity  to  the  agitated  pulp.  This 
flow  of  the  solution  is  in  addition  to  and  distinct  from  the  flow  due  to  the  con- 
stant addition  of  fresh  solvent  at  one  end  of  the  trough  and  the  drawing  off  of 
the  charged  solution  at  the  other  end  thereof;  but  it  will  be  seen  that  the  under- 
flow thus  effected  prevents  a  mere  surface  flow  of  the  solution  from  one  end  of  the 
trough  to  the  other.  On  the  contrary,  as  the  flow  from  the  respective  divisions 
of  the  trough  is  from  the  bottom  and  under  each  traveling  partition  or  blade,  the 
overflow  or  discharge  from  the  trough  at  the  end  is  necessarily  of  the  charged 
portion  of  the  solution.  It  will  be  seen  that  this  method  of  leaching  ores  places 
the  ore  and  the  solvent  under  perfect  control,  which  is  a  very  great  advantage 
with  respect  to  the  economical  leaching  of  ores.  There  is  an  agitation  and  con- 
stant shifting  of  the  pulp  in  the  solution,  which  very  much  accelerates  the  action 
of  the  solvent  and  shortens  the  time  required  therefor,  and  the  speed  of  the  con- 
veyer can  be  regulated  so  that  the  pulp  will  not  remain  in  the  tank  or  tanks  any 
longer  than  is  necessary,  and -yet  long  enough  for  the  extraction  of  all  value  there- 
from. On  the  other  hand,  the  flow  of  the  solvent  through  a  tank  can  be  gauged 
so  that  it  will  issue  from  the  tank  fully  charged  or  charged  to  the  degree  most 
profitable  under  all  the  conditions  of  the  case. 

576118 — February  2,  1897.  W.  F.  HEATHMAN.  Means  for  extracting  gold  and 
silver  from  sea-water. — In  order  to  extract  said  metals,  the  sea-water  or  salt  lake- 
water  is  passed  through  a  filter  made  of  carbon,  and  the  gold  and  sliver  held  in 
solution  in  the  sea-water  or  salt  lake-water  are  freed  from  the  chemical  combina- 
tions in  which  they  occur  in  the  water.  The  chlorides  and  bromides  of  gold  and 
silver  in  solution  when  passing  through  the  carbon  filter  are  decomposed  by  the 
reducing  power  of  the  carbon,  the  liberation  of  chlorine,  and  the  destruction  of 
the  bromine  combination,  with  the  result  that  metallic  gold  and  silver  are  pre- 
cipitated in  the  carbon  filter  and  deposited  in  the  pores  and  upon  the  surface  of 
the  carbon.  And  the  inventor  claims  a  tank  mounted  on  suitable  supports  and 
provided  in  its  side  with  an  inwardly  opening  valve  or  gate,  said  tank  having  a 
perforated  bottom,  and  a  filtering  medium  arranged  on  the  bottom  and  comprising 
alternating  layers  of  coarse  and  fine  carbon,  a  layer  of  wire-cloth,  and  a  perforated 
top  covering. 

584627 — June  15,  1897.  J.  J.  DEEBLE.  Apparatus  for  extracting  gold  from 
auriferous  material. — This  invention  has  been  devised  in  order  to  provide  a  machine 
for  use  in  the  extraction  of  gold  from  auriferous  material  by  the  aid  of  chemical 
solvents,  in  order  to  insure  the  particles  of  auriferous  material  being  brought  into 
intimate  contact  with  the  cyanide  or  other  solvent  solution.  It  includes  a  vat 
or  pan  to  receive  the  auriferous  material  to  be  treated,  having  at  or  about  its  cen- 
ter a  vertical  shaft  or  spindle  with  one  or  more  agitators  or  stirrers  attached  to 
its  lower  end.  Motion  is  imparted  to  this  shaft  or  spindle  by  bevel  gearing  or 
other  convenient  mechanical  contrivances,  and  means  are*  provided  for  reversing 
the  rotation  and  controlling  the  speed  of  the  agitators,  as  well  as  for  raising  or 
lowering  the  agitator  shaft  or  spindle.  These  means  may  consist  of  a  screw- 
threaded  lifting  rod  with  correspondingly  threaded  bevel  wheel  in  gear  with  a 
bevel  pinion  fitted  with  a  crank-handle,  whereby  it  may  be  rotated  in  the  required 
direction;  or,  if  preferred,  a  rack  and  pinion  may  be  used  for  the  purpose.  The 
inner  side  of  the  wall  of  this  vat  or  pan  is  provided  with  a  series  of  projections 
which  produce  eddies  or  swirls  in  the  material  under  treatment  as  it  is  carried 
round  the  vat  or  pan.  In  order  to  drain  or  draw  oft7  the  gold-bearing  solvent  from 
said  vat,  it  is  provided  with  a  vertically  sliding  valve  A  waste  discharge  valve 
may  also  be  provided  in  the  lower  part  of  the  vat  or  pan  for  the  purpose  of  enabling 
the  waste  material  to  be  sluiced  therefrom  after  the  gold  has  been  dissolved  and 
the  gold-bearing  solution  has  been  drawn  off  through  the  valve  above  referred  to. 

587408 — August  8,  1897.  H.  L.  SULMAN.  Method  of  recovering  precious  metals 
from  their  solutions. — This  invention  has  for  its  object  the  recovery  of  precious 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  355 

metals  from  solutions  of  the  same  by  means  of  a  new  and  improved  apparatus, 
the  apparatus  being  constructed  to  effect  the  deposition  or  "  precipitation  "  of 
the  precious  metal  or  metals  in  solution  upon  a  "  precipitating  "  substance  or 
"  precipitant  "  which  is  in  a  solid  but  more  or  less  finely  divided  state. 

The  apparatus  is  designed  to  recover  these  metals  from  solutions  of  their  haloids 
by  means  of  the  employment  therein  of  dense  but  more  or  less  finely  divided  car- 
bon, subsulphide  of  copper,  or  other  suitable  precipitant;  again,  also,  for  the 
recovery  of  the  same  metals  from  their  cyanide  solutions  by  means  of  the  finely 
divided  zinc  product  commercially  known  as  "  zinc  fume,"  and  generally  for  analo- 
gous requirements. 

It  is  necessary  that  whatever  the  nature  of  the  precipitant  used  and  the  degree 
of  fineness  to  which  it  is  found  desirable  to  reduce  it  primarily,  it  shall  be  of  greater 
specific  gravity  than  the  liquid  or  solution  desired  to  be  precipitated  by  it,  so  that 
the  precipitant  shall  tend  to  settle  from  the  liquor  by  gravitation.  Further,  it  is 
necessary  to  this  invention  that  the  solution  or  liquor  to  be  precipitated  shall  per- 
colate upward  through  the  mass  of  solid  finely  divided  precipitant. 

In  an  apparatus  with  parallel  vertical  sides  the  upward  flow  of  liquor  would 
tend  to  carry  off  finely  divided  particles  of  precipitant  unless  special  means  were 
taken  to  prevent  this.  Filters  tend  to  become  clogged  and  are  generally  useless 
for  this  purpose,  so  that  the  inventor  retains  the  particles  of  the  solid  precipitant, 
upon  whose  surfaces  the  precious  metals  are  in  course  of  deposition,  within  the 
apparatus  by  inducing  the  subsidence  of  them.  This  is  effected  by  continually 
reducing  the  upward  rate  of  liquor  flow,  which  is  secured  by  constantly  increasing 
the  area  of  the  liquor  column  as  it  rises  higher  in  the  apparatus. 

The  apparatus  takes  the  form  of  a  funnel.  The  liquor  enters  (under  a  suffi- 
cient pressure  or  "head")  through  the  bottom  orifice.  It  then  meets  with  and 
thoroughly  mixes  with  the  mass  of  finely  divided  precipitant  in  a  condition  of 
suspension  in  the  liquor.  The  solid,  finely  divided  particles  do  not  sink  against 
the  comparatively  rapid  inflow,  or  are  prevented  from  doing  so  to  any  extent, 
by  means  of  an  automatic  valve  of  ordinary  type.  By  this  intimate  admixture 
of  liquor  with  precipitant  the  deposition  of  the  precious  metals  in  solution  in  the 
former  is  effected  upon  the  minute  surfaces  of  the  latter.  It  now  only  remains 
to  remove  the  depleted  liquor  from  the  particles  of  the  solid  precipitant  containing 
the  gold,  silver,  etc.  As  the  liquor  continues  its  upward  flow  by  virtue  of  the 
continually  diverging  sides  of  the  apparatus  the  area  of  the  liquor  column  becomes 
greater  and  greater.  The  rate  of  the  vertical  upflow  is  thereby  correspondingly 
reduced.  This  continues  until  a  point  is  reached  at  which  the  upflow  is  vertically 
so  slow  that  the  finest  particles  are  able  to  settle  or  subside  against  it.  At  any 
point,  therefore,  above  this  limit  or  "zone,"  the  absolutely  clear  liquid  may  be 
drawn  o^  from  the  apparatus  free  from  suspended  particles  and  depleted  of  its 
precious-metal  contents. 

If  the  precipitation  of  the  precious  metals  be  deemed  to  be  incomplete  in  one 
apparatus,  owing  to  the  richness  of  the  original  liquor  or  to  other  causes,  the  outflow 
may  be  caused  to  pass  into  a  second  similarly  arranged  apparatus  or  through  two 
or  more  such  apparatus  placed  in  series;  but  in  general  one  apparatus  can  be  made 
to  secure  practically  perfect  removal  of  the  precious  metals  dissolved  in  a  given 
liquor  by  the  use  of  a  suitable  precipitant.  If  a  series  of  two  or  more  of  such  appa- 
ratus be  employed,  the  first  of  the  series  may  be  used  to  enrich  quantities  of  pre- 
cipitant which  have  only  been  partially  used  up  to  their  fullest  capacity  of  pre- 
cipitating the  precious  metals,  while  the  succeeding  members  of  the  series  are 
supplied  with  the  necessary  amounts  of  less  rich  or  quite  fresh  precipitant  in  order 
to  remove  any  remaining  traces  of  gold,  silver,  etc.,  which  may  escape  unpre- 
cipitated  in  the  outflow  from  the  first  apparatus.  The  poorer  precipitates  in  these 
last  apparatus  are  in  course  of  time  removed  through  the  bottom  of  the  apparatus 
and  transferred  to  the  first  one  of  the  series,  there  to  be  enriched  to  their  full 
capacity,  while  their  place  is  taken  by  fresh  quantities  of  poorer  or  quite  unused 
precipitating  agent,  and  so  on. 

When  the  precipitate  is  deemed  to  be  sufficiently  rich,  it  is  removed  from  the 
apparatus  by  a  " three-way  cock"  at  the  bottom  thereof,  or  by  other  suitable* 


356  APPENDIX. 

arrangement,  and  the  precious  metal  it  contains  finally  recovered  by  any  suitable 
method,  such  as  in  the  case  of  the  employment  of  a  carbon  precipitant  by  burning, 
or  in  the  case  of  the  use  of  a  zinc  precipitant  by  smelting. 

The  apparatus  is  also  supplied  with  a  small  central  funnel  for  the  introduction 
of  fresh  quantities  of  precipitant  from  time  to  time  to  the  point  of  maximum  pre- 
cipitating action  in  the  apparatus,  i.e.,  near  the  inflow.  By  providing  this  funnel 
with  a  bell-shaped  or  inverted  funnel  termination  a  sort  of  "chamber"  is  produced 
in  the  lower  part  of  the  apparatus  having  an  annular  space  for  the  passage  of  liquors 
between  the  rim  of  the  smaller  funnel  and  the  sides  of  the  large  one.  This  chamber 
is  of  considerable  aid  in  promoting  the  action  of  the  precipitant  by  keeping  the 
bulk  of  it  constantly  near  the  liquor  inflow  and  securing  perfect  admixture  by 
means  of  the  vortex  currents,  etc.,  it  induces.  It  is  further  desirable  to  break 
up  the  rapid  rush  of  inflowing  liquors  at  their  point  of  entry  into  the  apparatus 
and  to  secure  their  subdivision  and  intimate  admixture  with  the  precipitant  as 
early  as  possible.  This  is  effected  by  capping  the  end  of  the  inlet  pipe  with  a 
small  perforated  cone  or  "distributer."  The  perforations  may  be  from  one-fourth 
to  one- tenth  the  diameter  of  the  inlet  pipe,  but  their  total  area  must  be  larger  than 
that  of  the  sectional  area  of  the  pipe.  The  holes  may  be  bored  in  a  direction 
perpendicular  to  the  cap  cone  or  they  may  be  made  "tangential,"  i.e.,  bored  at 
a  tangent  to  the  internal  circumference  of  the  cone,  thus  securing  a  rotary  initial 
flow  of  the  inflowing  liquors  instead  of  a  series  of  straight  streams.  In  the  major- 
ity of  cases,  however,  perpendicular  bore  holes  answer  equally  well. 

The  clear  precipitated  liquor  may  be  drawn  off  at  any  point  above  the  limit 
of  subsidence  either,  by  a  pipe,  or,  preferably,  by  allowing  it  to  flow  equally  over 
the  rim  circumference  of  the  apparatus.  The  latter  method  secures  the  quieter 
and  more  uniform  outflow  and  does  not  disturb  the  top  layers  of  liquor  under- 
going final  subsidence  by  establishing  a  quick  current  in  one  particular  direction. 

If  desired,  the  rim  may  be  encircled  with  a  filter-screen  of  lawn,  calico,  or  other 
filtering  or  straining  medium,  so  as  to  retain  within  the  apparatus  any  particles 
of  precipitant  which  may  be  floated  or  "buoyed  up"  by  bubbles  of  air  or  other 
gas. 

The  clear  liquors  passing  over  the  rim  and  through  the  precautionary  filter  or 
strainer  fall  into  and  are  collected  by  a  circular  trough  or  "launder,"  attached 
to  the  apparatus  below  the  rim,  whence  they  are  conveyed  away  by  a  pipe.  As 
before  stated,  this  may  lead  into  a  storage-vat  or  into  another  similar  apparatus, 
or,  if  deposition  of  the  floating  particles  is  not  absolutely  complete,  into  any  suitable 
type  of  apparatus — such,  for  example,  as  the  slat-partitioned  tank  used  for  freeing 
softened  water  from  traces  of  deposit — where  subsidence  is  finally  rendered  abso- 
lute. In  most  cases  where  the  traces  of  precipitant  have  escaped,  I  have  secured 
perfect  final  subsidence  by  allowing  the  liquors  to  flow  through  a  shallow  tank 
of  from  four  to  six  times  the  area  of  the  top  of  the  precipitating  apparatus  before 
passing  them  direct  to  the  storage  liquor  vats. 

Such  an  apparatus  as  is  described  is  termed  a  "  precipitating  cone."  It  may 
be  constructed  of  any  suitable  material,  such  as  wood,  stoneware,  galvanized 
iron,  etc.,  according  to  the  nature  of  the  liquor  or  precipitant  it  is  designed  to 
treat.  Its  action,  until  the  charge  of  precipitant  it  contains  is  exhausted  and 
requires  renewal,  is  perfectly  automatic  and  continuous.  Its  capacity,  its  height, 
the  angle  of  its  f'des,  the  ratio  diameter  of  inflow  pipe  to  top  area  of  cone  will 
naturally  vary  with  the  volume  of  liquor  to  be  dealt  with,  the  rate  and  head  of 
liquor  inflow,  the  relation  of  the  specific  gravity  of  the  liquor  to  that  of  the  finely 
divided  precipitant,  the  actual  coarseness  or  fineness  of  the  particles  of  the  latter, 
and  so  on.  These  data  may  be  calculated  or  decided  by  preliminary  experiment 
in  any  particular  case.  As  an  example,  however,  of  the  application  of  this  in- 
vention to  the  recovery  of  gold  bullion  from  cyanide  solutions,  the  following  dimen- 
sions of  the  apparatus  are  cited:  For  a  flow  of  from  600  to  800  gallons  per  hour 
B  depth  of  5  feet,  with  a  top  diameter  of  5  feet,  is  amply  sufficient.  The  diameter 
of  the  inlet  pipe  is  from  1-J  to  If  inches,  according  to  the  head  of  the  inlet  liquor, 
Awhile  the  perforations  of  the  cap  cone  or  distributer  are  three-sixteenths  of  1  inch 


PATENTS  RELATING  TO  CYANIDE  PROCESSES  357 

in  diameter.     The  charge  of  zinc  fume  in  such  an  apparatus  varies  from  5  to  30 
pounds,  according  to  requirements. 

587874 — August  10,  1897.  E.  D.  SLOAN.  Barrel-filter. — The  object  of  this 
improvement  is  to  provide  a  suitable  filter-barrel,  with  a  durable  and  highly 
effective  filter,  at  comparatively  low  cost.  With  a  view  to  securing  the 
desired  ends  the  usual  trunnioned  iron  barrel  is  lined  with  lead.  The  framing 
of  the  filter-bed  is  composed  wholly  of  suitable  wood  capable  of  fairly  resist- 
ing the  action  of  chlorine  and  acids,  and  which  may  be  filled  with  suitable 
matter  to  enable  it  to  better  resist  the  destructive  action  of  the  corrosive  solutions. 
The  filtering  medium  is  composed  of  material  which  resists  the  solutions,  is  well 
protected  against  undue  abrasion  due  to  the  action  of  the  solid  matter  during 
the  rotation  of  the  barrel,  and  it  has  its  filtering  area  supported  to  enable  it  to 
safely  bear  the  overlying  contents  of  the  barrel  by  an  underlying  floor  of  such 
metal  as  will  practically  resist  the  action  of  chlorine  and  sulphuric  acid — as,  for 
instance,  a  lead  floor — and  the  latter  is  freely  perforated  to  admit  of  the  prompt 
discharge  of  the  filtered  liquid.  The  filtering  surfaces  are  flat,  and  hence  the  body 
of  any  woven  filtering  medium  is  maintained  in  a  condition  more  favorable  to  the 
passage  of  the  liquid  than  would  be  the  case  if  it  occupied  a  curved  line  and  said 
surfaces  were  concave  in  conformity  with  the  interior  contour  of  the  barrel.  The 
framing  of  the  filter-bed  involves  inexpensive  straight  work,  as  distinguished  from 
the  curved  or  segmental  work  in  framing,  which  is  made  to  conform  to  the  interior 
of  the  barrel  as  heretofore,  and  the  filter-framing  is  constructed  in  parts  which 
are  so  interlocked  as  to  secure  rigidity,  but  which  may  be  readily  applied  to  or 
removed  from  the  barrel  by  way  of  the  usual  manhole  and  without  deranging 
the  lead  lining  or  the  means  by  which  the  lining  is  clamped  to  the  barrel. 

597372 — January  11,  1898.  P.  J.  DONOHUE  and  J.  F.  CORKER.  Precipitating 
safe. — The  combination  with  a  closed  vessel  or  standpipe  provided  with  a  normally 
closed  outlet  at  its  bottom  for  the  precipitate  and  having  a  body  or  column  of 
zinc  filings  or  like  material  in  its  upper  part,  adapted  as  corroded  to  fall  into  the 
lower  part,  of  means  for  supplying,  under  pressure,  the  solution  containing  the 
precious  metal  to  the  lower  end  of  said  body  or  column  of  filings  or  like  material, 
to  cause  the  corrosion  or  oxidation  thereof,  whereby  such  corroded  or  oxidized 
portions  will  gradually  precipitate  to  the  bottom  of  the  vessel  or  standpipe  and 
the  fresher  portions  of  the  filings  or  like  materials  be  exposed  to  the  ascending 
solution. 

606810 — July  5,  1898.  J.  W.  PACK.  Recovery  of  gold  from  waste  solutions  of 
chlorinaiion  works. — A  means  for  recovering  gold  from  waste  solutions  of  chlorina- 
tion  works,  consisting  of  a  tank  having  an  inlet  passage  at  the  lower  portion  and 
an  outlet  passage  at  the  upper  portion  and  having  metallic  aluminum  contained 
therein,  and  intermediate  between  the  inlet  and  outlet  passages  of  the  tank,  and  a 
filter  fixed  within  the  tank  between  the  metal  and  the  outlet  passage  and  having 
its  lower  side  coated  with  a  substance  which  will  arrest  the  fine  precipitated  gold 
and  prevent  it  from  passing  off  with  the  liquid. 

608554 — August  2,  1898.  R.  MOODIE.  Washing  or  leaching  apparatus. — In 
an  apparatus  for  washing  or  leaching,  a  series  of  cells,  one  of  which  is  a  dry 
cell  and  the  others  of  which  contain  washing  or  leaching  liquid,  means  for  intro- 
ducing the  material  to  be  washed  into  the  dry  cell,  an  oscillating  shaft  extended 
longitudinally  of  the  series  of  cells,  means  operated  by  said  shaft  to  transfer  the 
material  from  the  dry  cell  to  the  washing  cell  next  in  series,  arms  attached  to  the 
oscillating  shaft  and  extending  one  into  each  washing  cell,  and  scoops  on  said  arms. 

608945 — August  9,  1898.  H.  B.  WILLIAMS.  Lixiviation  apparatus — In  a 
lixiviation  apparatus,  the  combination  of  a  vertical  series  of  annular  tanks 
arranged  one  above  another  and  each  provided  with  an  exit  through  which  ore 
or  other  substances  may  be  discharged  into  the  tank  beneath,  each  tank  bottom 
being  provided  with  an  ascending  incline  leading  to  one  side  of  the  tank  exit  and 
having  a  descending  incline  on  the  other  side,  means  for  feeding  ore  into  the  top- 
most tanks,  pipes  for  conveying  leaching  solution  into  the  several  tanks  separately, 
the  feed  of  the  ore  to  be  continuous  and  the  feed  of  the  solution  to  be  continuous 
or  intermittent,  filters  located  in  the  several  annular  tanks,  and  automatic  scraping 


358  APPENDIX. 

and  stirring  mechanism  to  cause  the  ore  and  solution  to  be  moved  around  each 
annular  tank  and  over  the  filter  therein. 

610596— September  13,  1898.  R.  AYMER  and  D.  J.  NEVILL.  Filter-frame. 
— In  a  filter-barrel,  the  combination  of  a  rubber  grating  having  a  corrugated 
surface  in  contact  with  the  curved  inner  lining  and  periphery  of  said  filter-barrel 
adapted  to  allow  the  filtering  solutions  to  run  along  and  down  the  lining  of  said 
barrel,  a  perforated  bedplate  of  glass  or  porcelain  curved  concentric  with  the  inner 
periphery  of  said  barrel  and  resting  on  said  rubber  grating,  a  filtering  medium 
on  said  glass  bedplate,  a  curved  glass  grating  resting  on  said  filtering  medium, 
two  oppositely  disposed  cleats  secured  lengthwise  of  said  barrel  to  its  inner  periphery 
adjacent  to  the  ends  of  said  curved  glass  bedplate  and  grating,  and  wedge  keys 
between  said  ends  and  said  cleats  adapted  to  key  said  members  against  the  barrel. 

611515 — September  27,  1898.  J.  P.  SCHUCH,  Jr.  Means  for  extracting  precious 
metals. — In  a  metallurgical  apparatus  for  treating  ore  by  a  cyanide  solution,  a  tilt- 
able  tank  comprising  a  suitable  support,  a  tank  body  having  a  discharge  gate  at  its 
rear  end  and  pivoted  to  a  support  at  a  point  between  its  centre  and  the  front  end, 
a  drain  device  in  the  bottom  of  the  tank  for  drawing  off  the  cyanide  solution, 
holding  springs  mounted  on  the  support  and  engaging  with  the  tank  body  at  points 
between  its  discharge  end  and  the  pivotal  connection  thereof  with  the  support, 
and  means  for  retracting  the  holding  springs  from  engagement  with  the  tank  body. 

611935 — October  4,  1898.  J.  POOLE.  Process  of  and  apparatus  for  treating  ore 
tailings. — For  the  continuous  treatment  of  pulps,  slimes,  tailings,  and  the  like  with 
cyanide  and  similar  solvent  solutions  and  in  combination,  a  series  of  shallow  tray- 
like  baths,  a  rake  in  each  bath  of  the  series  for  reciprocating  the  rakes,  an  overflow 
chute  at  the  end  of  the  series,  settling-tanks  to  receive  the  overflow  from  the  chutes, 
means  for  separately  discharging  the  solid  and  liquid  contents  of  the  tanks,  con- 
veyers adapted  to  raise  the  solid  contents  from  one  tank  after  discharge,  a  launder 
in  which  such  contents  are  received  and  in  which  they  may  be  further  treated 
with  a  solvent  solution  or  wash,  and  a  further  settling-tank  for  receiving  the  dis- 
charge from  the  launder. 

615968 — December  13,  1898.  T.  CRANEY.  Apparatus  for  treating  ores,  etc. — 
In  an  apparatus  for  treating  ores,  the  combination  of  a  tank  adapted  to  contain 
a  body  of  the  ore  to  be  treated,  devices  for  feeding  ore  into  the  top  of  said  tank 
and  discharging  it  from  the  bottom  thereof  at  a  point  above  the  tank  in  a  con- 
tinuous manner,  a  solvent  supply  reservoir,  a  receiver  connections  between  the 
tank  and  said  supply  reservoir,  and  receiver  for  producing  a  continuous  flow  of  the 
solvent  through  the  tank  in  a  direction  opposite  to  that  of  the  movement  of  the 
ore,  an  endless-chain  carrier  in  proximity  to  the  tank  and  having  draining  buckets 
adapted  to  receive  the  ore  discharged  from  the  tank,  means  for  discharging  a  liquid 
upon  the  drainage  buckets,  and  means  for  collecting  the  drainage  from  the  buckets 
and  returning  it  to  the  aforesaid  supply  reservoir. 

617029 — January  3,  1899.  W.  A.  K 6 NEMAN  and  W.  H.  HARTLEY.  Apparatus 
for  separating  liquids  from  solids. — The  method  of  abstracting  liquid  from  finely  pul- 
verized ore,  ore  slimes,  or  other  solids  impervious  to  percolation  with  which  the 
liquid  is  mixed,  which  consists  in  subjecting  the  mixture  to  gaseous  pressure  ap- 
plied above  the  same,  and  simultaneously  to  the  action  of  a  partial  vacuum  ap- 
plied below  the  same,  removing  a  portion  of  the  liquid  by  filtration  below  the  body 
during  compaction  of  the  solids,  and  collecting  and  abstracting  by  pressure  the 
remaining  liquid  above  the  compacted  solids. 

617497 — January  10,  1899.  P.  ARGALL.  Cyanide  -filter-tank. — In  a  cyanide 
filter-tank,  a  vertical  metallic  side  or  wall,  a  horizontal  bottom  secured  thereto, 
having  a  central  opening,  a  packing  ring  secured  to  the  inside  of  said  wall,  near 
the  bottom,  with  a  spacing,  a  system  of  level  joists  converging  from  the  perimeter 
toward  the  center,  upon  said  horizontal  bottom,  a  plastic  filling  between  said 
joists  sloping  downward  from  the  packing  ring  regularly  toward  the  central  open- 
ing, a  level  floor  with  interstices  laid  upon  said  joists,  permeable  filtering  material 
upon  said  floor,  and  a  covering  of  textile  fabric,  the  outer  margin  of  which  is  packed 
into  the  crevice  between  the  packing  ring  and  the  vertical  wall. 

618622 — January  31,  1899.  P.  SOMERVILLE.  Apparatus  for  extracting  metals. — 
An  apparatus  for  extracting  metals,  consisting  of  parallel  barrels  having  annular 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  359 

disks  closing  one  end  with  central  inlet  openings  for  the  material,  a  framework 
and  roller  support  for  said  barrels,  means  whereby  the  barrels  are  rotated  in  oppo- 
site directions,  spiral  flanges  fixed  to  the  interior  of  the  barrels  for  advancing  the 
material  therethrough,  devices  for  feeding  material  and  fluid  matter  to  the  upper- 
most barrel,  means  for  separating  the  coarse  from  the  fine  material  and  delivering 
them  separately,  and  means  for  transferring  material  from  the  discharge  end  of 
one  barrel  into  the  inlet  end  of  the  barrel  below. 

619211 — February  7, 1899.  A.  M.  NICHOLAS.  Filtering  apparatus  for  separating 
gold-  and  silver-bearing  solutions. — This  invention  has  been  devised  for  the  pur- 
pose of  providing  means  whereby  solids  or  insoluble  material  may  be  separated 
from  liquids  carrying  same  in  suspension,  but  more  particularly  for  the  purpose 
of  providing  means  whereby  the  separation  of  gold  and  silver-bearing  solutions 
from  tailings,  slimes,  pug,  or  pulverized  ore  may  be  carried  on  continuously  and 
in  such  a  way  that  a  clean  or  partially  clean  filter-cloth  will  be  continuously  brought 
into  operation  without  necessitating  stoppages  for  recharging,  as  required  with 
the  appliances  at  present  in  use. 

The  essential  feature  of  the  invention  consists  in  the  use  of  a  rotating-wheel, 
disk,  or  table  formed  with  a  series  of  air-tight  compartments  covered  with  cloth 
or  other  filtering  material  supported  upon  a  metal  sqreen  or  perforated  plate  and 
adapted  to  be  automatically  placed  in  communication  with  a  vacuum  pump  in 
turn  for  a  sufficient  time  to  enable  the  liquid  to  be  drawn  through  the  filtering 
material,  leaving  the  solid  constituents  upon  the  filtering  surface,  whence  they 
can  subsequently  be  removed  by  brushes,  jets  of  water,  scrapers,  or  similar  con- 
trivances, provision  being  made  for  automatically  allowing  air  to  enter  into  the 
various  compartments  at  the  desired  period  of  the  operation  to  facilitate  the  removal 
of  the  solids  from  the  outer  surface  of  the  filtering  material. 

620660 — March  7,  1899.  J.  LUCE.  Apparatus  for  treating  ores  by  lixivia- 
tion. — In  a  tank  for  the  treatment  of  ores,  a  lining  composed  of  asbestos  applied 
to  the  inner  side  of  the  tank,  the  notched  or  recessed  boards  applied  inside  of  the 
asbestos,  and  the  steam  pipes  placed  in  the  notches  in  the  boards,  combined  with 
two  thicknesses  of  grooved  perforated  boards,  and  the  layers  of  cloth  between 
the  boards. 

623465 — April  18, 1899.  G.  S.  DUNCAN.  Apparatus  for  separating  gold-  and 
silver-bearing  solutions  from  ores  or  slimes. — Hitherto  upward  percolation  has  been 
used  for  the  displacement  of  the  various  gold-  and  silver-bearing  solutions  in  the 
treatment  under  the  cyanide  or  other  similar  processes  of  tailings  or  free  leaching 
ores  which  are  not  in  the  form  of  slimes.  With  this  upward  percolation  false  bot- 
toms for  the  vats  with  webbing  upon  them  have  been  used  and  the  solutions  have 
been  introduced  underneath  these  false  bottoms,  which  have  acted  as  distributors 
therefor  and  allowed  them  to  pass  evenly  up  through  the  free  leaching  ore,  dis- 
placing the  gold-  and  silver-bearing  solution  contained  therein.  This  false  bot- 
tom and  webbing  are  adapted  for  use  with  free  leaching  ores  only  and  cannot  be 
employed  for  displacing  solutions  used  in  treating  very  finely  crushed  ores  or  limes 
which  do  not  leach  freely.  /\  * 

The  present  invention  has  been  devised  in  order  that  the  various  solutions 
may  be  displaced,  as  above  described,  from  finely  crushed  ore  or  slimes,  without 
the  aid  of  any  false  bottom  and  filtering  webbing.  And  the  inventor  claims,  in 
an  apparatus  for  separating  solutions  of  the  precious  metals  from  residual  ores 
and  slimes,  the  combination  with  a  leaching-  and  displacement-tank  or  vat  and 
with  a  vat  to  hold  said  solutions,  the  latter  being  placed  at  a  higher  level  than 
the  former,  of  a  series  of  pipes  to  convey  said  solutions  from  the  higher  vat,  the 
discharge  ends  of  said  pipes  entering  the  leaching-vat,  a  series  of  hoods  having 
slightly  arched  portions  which  overlie  the  said  discharge  ends,  and  stirring  arms 
radiating  from  a  central  shaft  in  said  vat,  the  arched  portions  of  the  hoods  being 
arranged  in  radial  lines,  or  at  right  angles  to  the  movement  of  currents  set  up  by 
the  stirring  arms. 

623772 — April  25,  1899.  A.  F.  DUEY.  Apparatus  for  leaching  ores.— A  device 
for  treating  pulverized  ores,  comprising  a  leaching-tank,  an  air-compressor,  a 
tank  for  storing  the  leaching  liquid,  a  perforated  pipe  in  the  bottom  of  the  leach- 


360  f  APPENDIX 

ing-tank,  connections  from  the  air-compressor  and  liquid-storing  tank  to  the  per- 
forated pipe,  a  perforated  drainage  pipe  in  the  bottom  of  the  tank,  and  a  layer 
of  filtering  material  about  said  pipe. 


? — May  9]  1899.  C.  H.  PEAD.  Slime  filter. — The  apparatus  consists 
of  a  tank  fitted  with  a  hood  of  conical  or  any  other  convenient  form.  The  sides 
of  the  tank  project  above  the  point  of  attachment  of  the  hood,  so  as  to  form  an 
annular  space  to  act  as  a  receptacle  forming  a  launder  for  discharge  of  the  clear 
liquid.  In  the  center  of  the  hood  is  an  opening,  around  which  is  riveted  or  bolted 
a  frame  or  seating  arranged  to  carry  a  niter  composed  of  one  or  more  layers  of 
niter-cloth  or  any  other  well-known  filtering  medium.  The  filter  is  kept  in  place 
by  means  of  a  protective  gird  of  clamp  of  suitable  form  and  strength  to  resist  the 
effective  pressure  from  the  interior  of  the  tank.  A  number  of  small  distribution 
pipes  set  at  such  an  angle  as  to  cause  the  slimes  to  impinge  on  the  under  surface 
of  the  filter  are  connected  to  the  seating  of  the  latter,  through  which  they  pass. 
They  are  connected  to  a  main  distributer,  which  in  turn  is  connected  with  the 
delivery-pipe  or  column  of  the  slime-pump.  One  or  more  taper-shaped  plugs 
or  cores  constructed  of  light  steel  tubes,  their  number  varying  according  to  the 
.size  of  the  tank,  pass  through  the  hood  and  extend  to  the  bottom  of  the  tank. 
They  taper  from  about  18  inches  at  the  top  to  15  inches  at  the  bottom.  They 
are  fitted  at  their  upper  ends  with  a  flange,  to  which  is  attached  a  shackle.  Their 
lower  ends  are  closed  by  means  of  a  dished  bottom  riveted  in  place  and  having 
a  strong  bolt  or  stud  fitted  to  its  center.  Each  plug  or  core  rests  on  a  seating 
fitted  to  the  outside  of  the  hood  and  through  which  the  plug  or  core  posses.  The 
seating  is  attached  thereto  by  means  of  its  flange. 

In  the  bottom  of  the  tank  and  directly  under  the  aperture  in  the  hood  through 
whi2h  the  plug  or  core  passes  is  a  discharge  door  of  the  ordinary  manhole  or  other 
convenient  type.  The  end  of  each  plug  or  core  passes  easily  into  the  discharge 
opanin^,  and  the  discharge  door  is  drawn  up  onto  its  seating  or  joint  by  means 
of  the  bolt  or  stud  on  bottom  of  the  plug  or  core  and  by  its  nut.  The  plugs  or 
cores  when  in  place  and  holding  up  the  manhole  doors'  afford  an  effectual  means 
of  resistance  against  internal  pressure. 

A  special  pipe  is  arranged  and  fitted  to  the  upper  portion  of  the  tank  to  drain 
the  space  forming  a  launder  between  the  top  of  the  tank  and  the  upper  surface 
of  the  hood  and  to  conduct  the  liquid  portion  which  has  passed  through  the  filter 
to  the  precipitation  boxes  or  to  waste. 


? — May  9,  1899.  F.  A.  EDWARDES.  Apparatus  for  use  in  treating  metallic 
ores. — In  apparatus  for  use  in  the  treatment  of  metallic  ores,  the  combination 
with  an  annular  vat  having  a  stirrer  moving  therein  and  skimmers  attached  to 
and  moving  with  the  said  stirrer,  of  means  for  tipping  the  said  vat  for  discharging 
the  contents. 

624957 — May  16,  1899.  L.  H.  MITCHELL.  Tank-bottom  discharge  door. — A 
discharge  apparatus  for  tanks  provided  with  a  hollow  upper  portion,  a  base  having 
integral-bearing  zones  connected  thereto  at  one  end  thereof,  a  casting  having  an 
upper  annular  supporting  rim  and  adapted  to  receive  said  bearing  zones,  a  ring 
surrounding  said  casting,  devices  connecting  said  rim  and  ring  to  secure  the  casting 
in  position,  and  means  supported  by  said  casting  to  unseat  said  base. 

624.958 — May  16,  1899.  L.  H.  MITCHELL.  Tank-bottom  discharge  door. — A 
discharge  apparatus  for  tanks  consisting  of  a  casting  secured  in  the  bottom  of 
the  tank,  a  ring  below  the  tank  around  the  casting,  and  means  for  securing  the 
rim  and  ring  in  position,  a  funnel  above  the  casting,  a  base  connected  with  the 
lower  end  of  the  funnel  and  provided  with  an  annular  offset  or  shoulder,  a  pack- 
ing-ring within  the  offset,  and  adapted  to  rest  upon  the  rim  of  the  casting,  a  plate 
or  bar  bearing  against  the  rim  of  the  casting,  a  nut-carrying  screw  in  the  plate 
or  bar  adapted  to  engage  the  base  and  draw  the  same  within  the  casting,  a  brace 
or  clamp  connected  to  the  plate  or  bar  above  the  nut  on  the  screw,  and  means 
for  rotating  the  screw. 

639540 — December  19,  1899.  W.  DUNCAN.  Means  for  mixing  and  aerating 
sands  or  tailings  while  under  treatment  by  solvents. — Numerous  attempts  have  from 
time  to  time  been  made  to  secure  the  thorough  mixing  of  sands  and  tailings,  includ- 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  361 

ing  slimes,  with-  the  solvent  while  under  treatment  and  also  to  prevent  that  close 
packing  which  prevents  the  percolation  of  the  solvent  and  wash  liquors.  For 
this  purpose  vertical  vessels  with  vertical  agitators,  revolving  barrels,  and  air, 
steam,  and  water  jets  have  been  used,  but  these  means  have  not  been  as  efficient 
as  they  might  be. 

This  invention  relates  to  improved  mechanical  means  for  mixing  and  aerating 
"sands"  or  "tailings,"  by  which  terms  are  included  slimes,  sludges,  and  con- 
centrates, while  under  the  action  of  solvents,  whereby  time  is  saved  and  a  better 
extraction  is  obtained;  and  it  consists  of  a  semicircular  vat  provided  with  a  re  voluble 
agitator  composed  of  arms  arranged  helically  on  a  shaft  running  the  length  of 
the  vat.  At  one  end  of  the  vat  is  placed  the  fast  and  loose  pulleys  and  gear 
for  slowing  and  rotating  the  agitator,  while  at  the  opposite  end  a  series  of  taps 
are  provided  connected  to  the  vat  at  various  heights  and  to  pipes,  so  that  the 
liquor  can  be  drawn  off  at  any  desired  point  and  either  run  direct  to  the  sump  or 
through  a  filter  to  the  sump. 

641419 — January  16,  1900,  H.  C.  WHEELER.  Agitator. — In  an  agitator,  the' 
combination  of  the  vat,  the  track  provided  with  the  cog-rack,  the  carrier  pro- 
vided with  the  pinion  meshing  with  the  cog-rack,  the  first  driving-shaft  provided 
with  the  driving-pinion,  the  driven  cog-wheel  meshing  with  the  driving-pinion, 
the  gear-wheels  connecting  the  driven  cog-wheel  with  the  pinion  meshing  with 
the  cog-rack,  the  agitator-frame  journaled  or  pivoted  to  the  carrier-frame,  the 
second  driving-shaft  journaled  in  the  agitator-frame,  the  agitators  journaled  in 
the  agitator-frame  and  adapted  to  be  operated  by  the  second  driving-shaft,  inter- 
mediate gearing  connecting  the  second  driving-shaft  with  the  driven  cog-wheel, 
one  of  such  gears  being  journaled  with  its  axis  in  line  with  the  axis  of  the  pivotal 
support  of  the  agitator-frame,  and  means  for  rotating  the  first  driving-shaft. 

647358 — April  10,   1900.     D.   W.   BALCH.     LeacMng-tank. — A   tank  having  a 
bottom,  a  leaching  false  bottom  above  the  same,  and  vertical  filtering  partitions    \^> 
arranged  in  pairs  within  the  tank,  whereby  spaces  are  left  between  pairs  of  par- 
titions, and  other  spaces  are  left  between  members  of  such  pairs,  said  spaces  last 
named  all  communicating  with  the  chamber  between  the  bottom  and  false  bottom. 
647678 — April  17,  1900.     C.  W.  MERRILL.     Means  for  charging  leaching-vcts. — 
This  invention  relates  to  a  method  of  charging  ore  or  tailings  to  a  leaching-vat,      1 
which  process  is  a  step  in  the  treatment  of  said  ore  or  tailings  preliminary  to  the 
application  of  the  solvent  solution  in  cyanide,  hyposulphite,  or  other  hydrometal- 
lurgical  processes. 

It  consists  essentially  in    conveying    the    tailings    or  ore  by  any  well-known 
adaptable  mechanical  means  to  a  point  above  the  center  of  the  vat  to  be  charged 
arid  delivering  the  material  there  to  a  hopper,  which  feeds  a  revolving  chute  inclined 
at  an  angle  greater  than  the  natural  slope  of  the  material  to  be  handled,  and  with 
openings  adjustable  both  as  to  size  and  position,  through  which  the  material  to/o 
be  treated  falls  gently  into  the  vat  and  distributes  evenly,  thus  giving  a  charge'"' 
of  minimum  density  and  maximum  homogeneity,  the  conditions  most  favorable 
to  successful  leaching  and  dissolution  of  the  precious  metals. 

The  ordinary  method  of  charging  leaching-vats  is  from  cars  running  on  a  super- 
imposed track.  By  this  means  the  momentum  of  the  carload  of  tailings  or  ore 
dropping  through  five  or  more  feet  to  the  bottom  of  the  vat  is  such  as  to  produce 
considerable,  packing  and,  moreover,  an  uneven  packing  or  density.  For  instance, 
in  dumping  from  an  end  discharge  car  the  resultant  mass  of  ore  or  tailings  will 
take  the  form  of  a  cone  in  the  vat  and  the  maximum  density  will  be  in  the  center 
of  the  approximate  circle  forming  the  base  of  the  cone  and  will  decrease  along" 
the  radii  toward  the  circumference  of  this  circle.  Furthermore,  the  variation 
in  fineness  of  the  different  carloads  is  not  equalized,  and  a  vat  charge  of  ore  or  tail- 
ings results,  which  is  heterogeneous,  both  as  regards  density  and  as  regards  fine 
and  coarse  material.  Now,  first,  the  charge  of  ore  or  tailings  in  a  vat  should  be 
of  the  least  density  possible  to  obtain,  because  experience  has  demonstrated  that 
the  greater  the  permeability,  and  consequently  the  greater  the  amount  of  lixiviant 
possible  to  percolate  through  the  charge,  the  greater  the  extraction  of  the  precious 
metals  in  a  given  time,  or,  from  another  standpoint,  the  greater  the  permeability 
the  less  the  economic  period  for  leaching,  and  hence  the  less  the  cost  for  plant 


362  APPENDIX. 

and  subsequent  operation;  second,  the  charge  should  be  as  nearly  homogeneous 
as  possible  as  regards  both  density  and  size  of  material,  because  in  leaching  ores 
it  is  necessary  to  follow  solution  with  wash-water  to  replace  and  prevent  the  loss 
of  the  former  or  to  follow  one  lixiviant  with  another  of  different  strength  or  con- 
taining a  different  solvent,  and  in  doing  this  to  maintain  the  surface  of  demarca- 
tion between  the  one  and  the  other  as  nearly  a  horizontal  plane  as  possible  in  order 
to  minimize  the  mixing  of  effluent  solutions.  The  above  conditions  of  minimum 
density  and  maximum  homogeneity  are  produced  by  means  of  a  revolving  inclined 
wide  chute  with  small  openings  in  the  bottom,  adjustable  as  to  size  and  position 
transverse  to  the  direction  of  the  stream  of  ore  or  tailings.  By  means  of  this 
method  a  number  of  very  small  streams  of  ore  or  tailings  fall  gently  into  the  vat 
as  the  chute  revolves,  and  by  increasing  the  speed  of  revolution  a  carload  of  fine 
or  coarse  material  can  be  spread  over  the  whole  area  of  the  vat,  thus  giving  the 
smallest  possible  dimension  parallel  with  the  course  of  the  lixiviant. 

653631 — July  18, 1900,  J.  C.  WALLACE.  Filter  barrel  or  tank. — In  a  filter  barrel 
or  tank,  a  filtering  device  consisting  of  a  series  of  curved  metal  plates,  perforated, 
fastened  to  the  inside  wall  or  walls  of  said  barrel  or  tank;  a  filter-cloth  upon  the 
upper  surface  of  said  plates,  secured  thereon  by  a  series  of  imposed  metal  bars 
and  filling  strips  secured  in  position  by  bolts  or  other  fastening  devices  to  the  wall 
or  walls  of  said  barrel  or  tank. 

653684— July  17,  1900.  F.  H.  LONG!  Metallurgical  filter. — The  combination 
with  a  closed  vessel  having  a  filter  septum  and  a  regulated  outlet  port  for  the  fil- 
trate beyond  such  septum,  of  the  wash-water  pipe  connected  in  hydrostatic  column 
with  said  vessel  and  the  external  centrifugal  pump  joined  at  its  separate  sides  in 
closed  union  with  the  opposite  ends  of  the  vessel,  the  journal-box  for  said  pump- 
axle  being  furnished  with  a  water  column  pipe  to  counterbalance  the  hydrostatic 
pressure  at  the  vessel. 

654315 — July  24,  1900.  T.  E.  LEECE.  Apparatus  for  working  ores  of  valuable 
metals — This  invention  relates  to  an  apparatus  which  is  designed  for  working  the 
ores  of  valuable  metals,  and  is  especially  useful  for  separating  slimes  from  solutions 
in  which  they  may  occur,  and  also  for  separating  heavier  and  lighter  parts  under 
any  condition  in  which  they  may  be  found  associated. 

It  consists  essentially  of  a  tank  and  an  endless  traveling  belt  with  directing 
rollers,  by  which  one  portion  of  the  belt  is  caused  to  travel  through  the  tank  in 
close  proximity  with  the  bottom  and  the  other  part  is  guided  back  exterior  to 
the  tank  by  similar  rollers.  It  also  comprises  a  means  for  straining,  or  separating 
the  liquid  from  the  heavier  portions. 

660498. — October  23,  1900.  J.  A.  FLEMING.  Apparatus  for  leaching  ores.— 
In  an  ore-leaching  apparatus  the  combination  with  the  leaching-tank  having  a 
pulp  discharge,  of  the  conical  perforated  filtering-hopper  therein  having  the  dis- 
charge for  the  pulp,  means  by  which  to  maintain  air  pressure  below  the  diaphragm, 
whereby  to  control  the  flow  of  solution  through  it,  means  for  the  introduction  and 
withdrawal  of  chemicals  to  and  from  the  body  of  the  tank  above  the  filtering  dia- 
phragm, and  devices  for  controlling  the  discharge  of  the  pulp  from  the  tank. 

660499— October  23,  1900.  J.  A.  FLEMING.  Apparatus  for  leaching  ores.— 
An  ore-leaching  apparatus,  consisting  of  the  leaching-tank,  having  a  filtering- 
hopper  a  solution  discharge  below  said  hopper,  and  a  pulp  discharge  also  below 
said  hopper,  and  independent  of  the  solution  discharge,  a  washing-tank  below  the 
leaching-tank  and  in  position  to  receive  the  pulp  from  the  discharge  thereof,  and 
means  for  controlling  the  passage  of  the  pulp  from  the  leaching-  to  the  washing- 
tank. 

664059— December  18,  1900.  J.  P.  SCHUCH,  Jr.  Ore-mixing  machine. — 
Heretofore,  in  treating  gold-bearing  ores  by  the  common  cyanide  process,  the 
•ore  is  first  crushed,  dried,  and  rolled  to  a  proper  degree  of  fineness,  and  that  which 
requires  roasting  is  then  conveyed  to  the  roasters,  while  the  oxidized  ore,  which 
•does  not  require  roasting,  is  conveyed  to  the  bin  or  receptacle  therefor.  After 
the  portions  of  the  ore  to  be  roasted  have  passed  through  this  step  of  the  process 
the  same  is  conveyed  to  the  cooling-room  before  being  deposited  in  the  bin  or 
receptacle  referred  to  which  contains  the  ore  requiring  no  roasting.  All  of  the  ore 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  363 

is  then  removed  by  manual  labor  into  the  ordinary  stationary  cyaniding-tanks, 
and  after  these  tanks  are  filled  with  the  ore  the  cyanide  solution  is  introduced 
therein.  In  this  process  the  filled  cyanide-tanks,  with  the  solution  and  ore  therein, 
are  permitted  to  remain  filled  and  unmolested  for  a  sufficient  length  of  time  for 
the  solution  to  act  on  the  ore,  after  which  the  gold-bearing  solution  is  drawn  off 
and  allowed  to  flow  to  the  precipitation-room,  while  the  tailings  in  the  tank  are 
then  washed  with  water  and  shoveled  out  or  sluiced  out  when  this  is  possible. 
In  this  process,  which  is  the  one  usually  followed  out  in  extracting  gold  and  silver 
from  their  ores  by  the  use  of  cyanogen  containing  solvents,  the  percentage  ex- 
tracted rarely  exceeds  80  per  cent,  of  the  ore  value,  and  it  is  the  purpose  of  the 
present  invention  to  provide  means  whereby  a  larger  per  cent,  of  the  value  of  the 
ores  may  be  saved. 

To  this  end  the  invention  contemplates  an  improved  mixing-machine  which 
provides  for  a  thorough  aeration  of  the  ore  and  solution,  while  at  the  same  time 
providing  for  a  mixing  of  various  grades  of  ore  with  the  cyanide  solution,  so  as 
to  make  one  even  grade  out  of  ores  of  various  values.  And  the  inventor  claims, 
in  an  ore-mixing  machine,  an  open  tank  provided  at  the  bottom  with  a  solution 
drain,  a  perforated  false  bottom  arranged  within  the  tank  above  the  main  bottom 
and  supporting  filtering  material,  an  ore  discharge  pipe  communicating  with  the 
interior  of  the  tank  immediately  above  the  plane  of  the  false  bottom,  a  revoluble 
agitator  depending  within  the  tank  into  close  proximity  with  reference  to  the 
false  bottom,  and  a  plurality  of  air  jets  arranged  to  communicate  with  the  tank 
in  a  plane  intermediate  the  said  false  bottom  and  the  lower  end  of  the  agitator 
thereabove. 

664196— December  18,  1900.  J.  C.  WALLACE.  Filter-bed.— In  a  filter-barrel, 
a  filter-bed  consisting  of  a  series  of  metal  plates  having  drain  slots  or  perforations 
therethrough,  a  series  of  perforated  tiles  arranged  as  a  filtering  medium  upon 
and  supported  by  said  metal  plates,  a  series  of  metal-binding  strips  imposed  upon 
or  against  said  tiles;  together  with  suitable  means  for  fastening  or  confining  the 
same  together  and  to  the  inner  wall  of  a  filter-barrel  or  tank. 

671028 — April  2,  1901.  J.  R.  PHILLIPS.  Pulp  agitator. — This  invention  con- 
sists of  an  inclined  or  funnel-shaped  tank  or  containing  vessel  into  which  the  pulp 
is  placed  with  water,  cyanide  solution,  or  other  equivalent  liquid,  a  circulating-  or 
suction-  and  force-pump  by  which  the  surface  liquid  may  be  drawn  from  the  tank, 
and  a  pipe  extending  centrally  down  to  near  the  bottom  of  the  cone,  with  a  dis- 
charge nozzle  through  which  the  liquid  is  delivered  with  force,  so  as  to  flow  upward 
along  the  sides  of  the  funnel  and  through  the  material,  whereby  the  latter  is  loosened, 
agitated,  and  prevented  from  packing.  In  conjunction  with  this  may  be  used 
a  canvas  or  equivalent  filter  lining  for  the  funnel,  with  means  for  providing  a  space 
intermediate  between  it  and  the  sides  of  the  funnel  for  the  filtering  through  of 
water,  and  a  means  for  conducting  such  filtered  water  away  from  the  apparatus. 

680154 — August  6,  1901,  A.  D.  JANSEN.  Discharge  door  for  cyanide-tanks. — 
In  cyanide  treatment  the  sands  are  subjected  to  the  action  of  cyanide  solution, 
which  solution  after  the  proper  length  of  time  has  elapsed  is  drawn  off  through 
a  filter  composed  of  matting  or  some  similar  material  situated  at  the  bottom  of  the 
tank.  This  matting  or  filtering  material  does  not  rest  directly  on  the  bottom 
of  the  tank,  but  is  supported  by  a  grating  or  perforated  false  bottom  in  order  to 
allow  a  free  passage  for  the  solution  which  has  filtered  through.  That  portion 
of  the  tank,  therefore,  which  is  situated  over  the  discharge  door  has  no  grating 
or  filtering  material,  and  consequently  a  more  or  less  vertical  column  of  sand  is 
left  in  the  tank,  which  still  contains  cyanide  solution  with  gold  in  solution,  the 
result  being  that  this  portion  is  imperfectly  treated. 

The  object  of  this  invention  is  to  provide  a  door  so  constructed  that  a  piece 
of  matting  or  filtering  material  may  be  placed  upon  it  in  order  that  the  filtration 
of  the  solution  shall  be  just  as  complete  over  the  discharge  door  as  in  the  rest  of 
the  tank. 

This  invention  furthermore  relates  to  an  improved  construction,  whereby  the 
door  is  rendered  much  more  easily  closed  and  also  to  a  system  of  packing  the  same 
by  which  joint  between  the  door  and  the  bottom  of  the  tank  is  rendered  tight. 


364  APPENDIX. 

683412 — September  24,  1901.  A.  J.  PERRY.  Ore-separator. — The  object  of  this 
invention  is  to  introduce  a  mixture  of  steam  and  air  in  the  pulp,  whereby  the 
precious  metal  receives  a  quick  chemical  action,  with  the  result  that  considerable 
time  is  gained  over  the  method  heretofore  employed.  And  the  inventor  claims, 
in  a  leaching  apparatus,  the  combination  of  a  receptacle  for  holding  pulverized 
ore,  an  agitator  mounted  in  said  receptacle  and  having  a  series  of  radial  horizontal 
pipes  each  provided  with  a  series  of  perforations  at  one  side  thereof,  a  series  of 
scrapers  or  blades  mounted  on  said  agitator,  a  pipe  adapted  to  supply  to  said  agitator 
a  mixture  of  steam  and  air  from  a  proper  source,  and  means  adapted  to  rotate 
said  agitator  whereby  the  discharge  of  steam  and  air  through  the  perforations 
of  said  pipes  is  directed  toward  the  rear  while  the  said  scrapers  or  blades  are  moving 
in  the  opposite  direction. 

684654 — October  15,  1901.  C.  VOELKER.  Ore-filter. — The  extraction  of  valuable 
metals  from  ores  through  the  lixiviation  processes,  such  as  the  cyanide  and  others, 
although  allowing  the  advantageous  working  of  low-grade  ores,  still  has  one  fault, 
that  more  or  less  metal  remains  in  the  tailings,  and  thus  losses  occur  caused  by 
the  slimy  particles  contained  in  the  pulverized  ores  generated  from  clay,  talc, 
and  other  minerals  which  clog  up  the  meshes  of  the  filtering-cloth,  and  thus  pre- 
vent the  solution  from  going  through  freely.  In  such  apparatus  the  ore  is  intro- 
duced and  the  solution  added,  and  where  it  happens  that  the  ore  lies  in  different 
grades  of  value  inside  the  tank,  the  solution  cannot  dissolve  the  metalliferous 
particles  in  an  even  manner,  and  at  the  same  time  where  it  enters  first  it  will  affect 
the  pulp  more  thoroughly,  and  as  it  goes  down  to  the  bottom  will  take  the  slimes 
forming  with  it,  depositing  them  around  the  aperture  through  which  the  solution 
is  drawn  off,  and  even  several  after-leachings  will  not  remove  them.  To  over- 
come these  drawbacks  it  is  necessary  to  construct  a  mechanical  apparatus  which 
shall  possess  the  condition  of  letting  the  soluble  liquids  needed  to  dissolve  the 
metals  go  through  the  pulp  in  a  space  of  time  to  be  governed  by  the  operator. 
Some  ores  are  liable  to  contain  chemical  substances  retarding  the  effectiveness  of 
the  soluble  agent  used,  and  where  it  is  of  great  import  to  remove  them  as  quickly 
as  possible  to  keep  them  from  going  into  chemical  action  with  the  solution  used. 

The  object  of  this  invention,  therefore,  is  to  combine  the  above-mentioned 
conditions,  and  the  apparatus  can  be  used,  in  addition  to  other  milling-plants, 
to  receive  the  tailings  direct  from  the  mill.  The  filtrate  can  be  examined  in  regard 
to  the  valuable  mineral  matter  which  may  exist,  giving  the  metallurgist  the  means 
of  saving  the  valuable  salts  of  mercury,  copper,  silver,  gold,  and  the  like  which 
may  form  through  the  chemical  or  electrical  action  in  the  amalgamators  where 
such  are  used  and  where  the  extravagant  use  of  copper  sulphate,  mercury,  and 
salt  is  in  most  cases  the  cause  of  the  solubility  of  gold. 

The  inventor  claims:  An  ore-filter,  comprising  a  funnel-shaped  tank,  a  basket- 
pr  filter-holder  removably  arranged  in  said  tank  and  fitting  closely  against  its 
inner  wall,  a  filtering  textile  stretched  over  the  inner  surface  of  said  basket,  a  top 
or  hood  for  the  tank,  a  shaft  extended  downward  in  the  tank,  and  a  screw  mounted 
on  said  shaft  and  spaced  at  its  inner  edge  therefrom,  the  said  screw  having  the 
end  of  its  upper  turn  turned  downward. 

687920 — December  3, 1901 .  A.  D .  JANSEN.  A pparatus  for  charging  or  discharging 
cyanide-vats,  etc. — In  combination,  the  pair  of  tanks  situated  one  above  the  other, 
stirring  mechanism  for  said  upper  tank,  having  a  hollow  supporting  or  operating 
mechanism,  and  stirring  mechanism  in  said  lower  tank,  having  its  operating  mechan- 
ism in  line  with  the  hollow  mechanism  of  the  upper  tank,  and  means  for  raising 
said  operating  mechanism  of  the  lower  tank  into  said  hollow  mechanism  of  the 
upper  tank. 

688085 — December  3,  1901.  A.  G.  GOLDSOBEL,  W.  MUTTERMILCH,  and  C. 
JABLCZYNSKI.  Apparatus  for  the  recovery  of  precious  metals  from  photographic 
residuum. — The  combination  with  a  vessel  having  a  loose  lid,  a  spout  or  outlet 
for  the  outflow  of  liquid  and  a  conical  bottom  and  with  a  precipitating  material 
contained  in  said  vessel,  of  a  tube  having  a  funnel-shaped  end  reaching  within 
said  vessel,  and  of  a  second  tube  provided  with  a  cock  connecting  the  aforesaid 
precipitating  vessel  and  funnel-shaped  tube  with  a  second  vessel  or  receiver. 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.      365- 

689799 — December  24,  1901.  R.  L.  GRAVES.  Ore-leaching  apparatus. — The> 
apparatus  for  use  in  extracting  ores,  consisting  of  a  plurality  of  tanks,  a  pump, 
a  discharge-pipe  leading  from  said  pump  and  having  a  plurality  of  branches  lead- 
ing to  the  several  tanks  and  provided  each  with  a  discharge-pipe  which  may  be 
turned  axially  or  swung  vertically,  valves  controlling  the  several  branches,  and 
a  flexible  supply-  or  suction-pipe  leading  to  the  pump  and  arranged  to  be  shifted 
from  tank  to  tank,  levers  connected  with  the  several  discharge-pipes  whereby 
they  may  be  turned  axially,  and  means  connected  with  the  lower  ends  of  the  dis- 
charge-pipes whereby  they  may  be  swung  vertically. 

690375 — December  31,  1901,  G.  RUBSCH,  Jr.  Agitating-machine  for  cyaniding 
— An  agitating-machine  for  the  treatment  of  gold  and  silver  ore  by  the  cyanide 
process,  comprising  an  agitating-tank,  having  a  conical  bottom;  a  heating-chamber, 
surrounding  the  conical  bottom  of  the  agitating-tank;  means  to  heat  said  chamber, 
a  rotary  pump,  centrally  disposed  in  the  agitating-tank,  adapted  to  take  the 
solution  from  the  bottom  of  the  tank  and  discharge  it  above  the  top  thereof;  a 
rotary  deflector,  adapted  to  distribute  the  solution  over  a  stationary  deflector; 
and  a  stationary  deflector  affixed  to  the  casing  of  the  pump,  adapted  to  deflect 
the  solution  to  near  the  edge  of  the  agitating-tank. 

691706 — January  21,  1902.  F.  H.  LONG.  Metallurgical  filter. — The  com- 
bination of  a  vessel  having  a  conical  filter-septum  and  an  outlet-port  for  the  filtrate 
beyond  such  septum,  of  means  for  establishing  an  end-to-end  circulation  of  the 
vessel  contents  above  said  septum,  a  conical  spreader  and  an  oppositely  facing 
conical  baffle-plate  having  a  projecting  spiral  flange  successively  interposed  between 
the  ends  of  the  vessel  and  arranged  adjacent  to  said  conical  filter-septum  to  in- 
timately direct  such  circulation  over  the  surface  thereof. 

697178 — April  8,  1902.  E.  L.  SHARPNECK.  Apparatus  for  the  treatment  of  ores. 
— As  a  means  for  facilitating  the  dissolving  of  the  values  in  ores,  the  combination 
of  a  leaching-tank,  a  conduit  leading  from  and  discharging  directly  into  the  tank, 
and  means  in  the  conduit  connected  with  the  heating-medium  supply  for  agitating, 
circulating,  and  heating  the  liquid  contents  of  the  tank. 

698016 — April  22,  1902.  J.  J.  HERVEY.  Cyanide-tank. — Cyanide-tank  having 
a  tapering  bottom  and  a  central  cone  arranged  in  connection  with  the  bottom, 
an  annular  lining  arranged  in  the  tank  and  open  at  its  lower  end,  a  filtering-screen, 
connecting  the  lower  end  of  the  lining  and  the  central  cone,  the  air  and  water- 
pipes,  the  charging-  and  discharging-pipes,  and  the  forcing  means  connected  with 
said  pipes. 

699211 — May  6,  1902.  DE  W.  C.  MOSHER.  Barrel-filter. — The  combination 
with  the  lead  lining  of  a  filter-barrel,  of  filter-sections  or  plates  having  projections 
on  their  outer  sides  and  perforations  through  the  plates  between  the  projections, 
and  having  bent  ends,  whereby  the  plates  may  be  united  to  the  lining  by  burning. 

699212 — May  6,  1902.  DE  W.  C.  MOSHER.  Barrel-filter. — The  combination 
with  the  lining  of  a  filter-barrel,  of  perforated  filter-sections,  and  means  for  support- 
ing said  sections  and  securing  them  to  the  linings,  said  sections  having  their  ad- 
jacent ends  so  constructed  and  arranged  to  form  a  longitudinal  channel. 

701239 — May  27,  1902.  F.  D.  WOOD.  Means  for  working  ores  by  the  cyanide 
process. — An  apparatus  for  treating  ores  consisting  in  combination  of  a  plurality 
of  aligned  containing-tanks,  a  transversely  concaved  endless  belt  passing  through 
and  returning  beneath  each  of  said  tanks,  and  upon  which  the  ore  is  carried  each 
of  said  belts  discharging  its  load  upon  the  belt  of  the  next  succeeding  tank,  means 
for  driving  said  belts  in  unison,  means  by  which  said  belts  are  kept  transversely 
distended,  and  rollers  disposed  at  intervals  in  said  troughs  and  over  which  the 
belts  pass,  whereby  the  latter  are  given  an  undulatory  movement. 

702064 — June  10,  1902.  F.  H.  LONG.  Metallurgical  filter.— -In  metallurgical 
filters,  the  combination  with  the  closed  perforated  tank  having  an  internal  fabric- 
septum  with  stretcher-frame  therefore  to  rest  against  the  tank-walls  of  the  feed- 
pipe leading  into  the  tank-bottom  and  the  separate  wash-water  pressure-tube 
united  to  said  feed-pipe  between  the  inlet  and  outlet  valves  thereof. 

702490 — June  17,  1902.  R.  SEEM  AN.  ^  Apparatus  for  treating  copper  ores.  A 
plant  for  the  treatment  of  ores,  comprising  a  safety  vessel,  a  mixer  revolubly 


366  APPENDIX. 

mounted,  a  settler  revolubly  mounted  at  a  lower  level  than  the  mixer,  and  a  still 
revolubly  mounted  at  a  lower  level  than  the  settler,  and  pipes  connecting  the 
several  vessels  together,  the  portions  of  the  several  vessels  and  pipes  with  which 
the  ammoniacal  solution  of  copper  comes  in  contact  being  of  material  indestructi- 
ble by  such  solution. 

705589 — July  29,  1902.  A.  JAMES.  Apparatus  for  precipitating  gold  and 
silver  from  their  solutions. — In  the  precipitation  of  gold  and  silver  from  cyanide 
and  other  solutions  zinc  is  usually  employed  as  a  precipitant,  and  the  use.  of  iron 
vessels  containing  the  solutions  has  been  found  objectionable,  because  the  iron 
being  electronegative  to  zinc  a  galvanic  action  is  set  up  between  the  vessel  and 
the  zinc,  which  causes  the  precious  metal  to  be  deposited  upon  the  vessel  instead 
of  upon  the  precipitant.  Owing  to  this  difficulty  the  general  practice  has  been 
to  use  vessels  constructed  of  wood  or  earthenware,  which  are  inconvenient  and 
do  not  facilitate  the  cleaning-up  operation. 

The  object  of  this  invention  is  to  avoid  these  objections. 

To  this  end  the  invention  consists  in  a  metallurgical  filter  for  separating  precious 
metal  from  a  solution  containing  it,  consisting  of  a  metallic  vessel  and  a  zinc  sponge 
disposed  therein,  said  vessel  having  an  inner  coating  of  enamel,  whereby  galvanic 
action  between  the  metallic  vessel  and  the  zinc  is  prevented  and  deposit  of  precious 
metal  on  the  vessel  avoided. 

705726 — July  29,  1902.  J.  C.  WALLACE.  Filter-bed. — In  a  filter-bed,  the  com- 
bination of  a  corrugated  filter-sheet  or  blanket  having  numerous  perforations 
through  the  lower  arcs  of  said  corrugations ;  a  series  of  transverse  supporting 
bars  formed  to  fit  under  and  receive  the  corrugated  contour  of  said  filter-sheet; 
a  series  of  superimposed  binding  strips  or  bars  with  transverse  corrugations  and 
slotted  ends;  two  longtiudinal  side  binding  strips  or  bars,  and  bolts  adapted  to 
holding  the  several  members  together  and  in  place  within  a  filter-barrel  or  tank. 

706334 — August  5,  1902,  G.  MOORE.  Apparatus  for  leaching  ores,  etc. — In 
dissolving  the  soluble  portions  of  ores,  furnace  products,  and  other  like  materials 
it  has  always  been  difficult  in  one  operation  to  dissolve  the  final  traces  of  the  soluble 
portions  and  at  the  same  time  completely  utilize  the  dissolving  power  of  the  acid 
alkali.  The  weakening  of  the  acid  or  alkali  by  its  dissolving  action  makes  its 
action  less  energetic  toward  the  finish  of  the  operation  at  the  very  time  when  the 
more  difficult  soluble  particles  needing  the  most  energetic  dissolving  action  are 
acted  upon.  This  not  only  causes  loss  of  reagent,  but  also  further  loss  on  account 
of  the  poor  extraction  of  the  soluble  elements  desired.  Also,  in  the  case  of  ores 
of  a  talcose  or  slimy  nature  the  talcose  portions  in  the  form  of  slimes  prevent  per- 
colation of  the  solutions  in  tanks  by  clogging.  These  slimes  should  be  separated 
and  filtered  separately  by  known  methods.  Then  the  remaining  portion  will 
easily  allow  percolation. 

The  object  of  this  invention  is  to  provide  an  improved  apparatus  for  the  pur- 
pose of  overcoming  these  difficulties;  and  with  this  object  in  view  the  invention 
consists,  primarily,  in  a  hollow  truncated  cone  mounted  to  rotate  about  a  cen- 
tral horizontal  axial  line,  provided  with  an  opening  at  one  end  to  receive  the  mate- 
rial to  be  acted  upon,  an  opening  at  the  opposite  end  to  receive  the  fluid  solvent, 
means  for  actuating  the  material  through  the  cone  in  one  direction  and  means  for 
actuating  the  fluid  solvent  through  the  cone  in  the  opposite  direction  simultaneously 
with  the  passage  of  said  material. 

706472 — August  5,  1902.  A.  E.  JOHNSON.  Filter-bed  for  chlorination  barrels. — 
The  combination  with  a  chlorination  barrel  or  tank  of  a  filter-bed  placed  therein 
and  composed  of  a  series  of  bars  placed  side  by  side  and  having  grooves  in  their 
sides  forming  spaces  for  filtering  material,  the  corners  of  the  bars  being  cut  away 
to  permit  insertion  of  the  filtering  material  after  the  bars  are  placed  side  by  side, 
and  binding  strips  located  at  the  ends  of  the  bars  and  covering  the  filling  open- 
ings, the  said  strips  being  secured  to  the  barrel  to  hold  the  filter  in  place,  an  out- 
let being  formed  in  the  barrel  below  the  filter. 

708494 — September  2,  1902.  J.  RANDALL.  Apparatus  for  extracting  metals 
from  ores. — In  an  apparatus  for  treating  ores,  the  combination  of  a  series  of  tanks 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  367 

with  a  series  of  agitators  above  said  tanks  and  discharging  into  the  same,  so  arranged 
that  the  overflow  of  the  solvent  fluid  from  each  tank  discharges  into  the  agitator 
over  the  next  adjacent  tank  and  from  thence  into  the  latter,  and  means  for  con- 
veying the  ore  from  the  bottom  of  each  of  said  tanks  into  the  agitator  directly 
above  the  adjacent  tank  for  discharge  into  the  latter. 

709135 — September  16,  1902.  J.  BROWN.  Ore-leaching  apparatus. — An  appa- 
ratus for  leaching  ores,  comprising  a  tank  adapted  to  contain  water  or  other  liquid, 
a  conduit  connected  to  and  extending  upwardly  from  the  tank  and  having  the 
plurality  of  chambers,  a  hopper  disposed  above  the  upper  chamber,  ball-valves 
for  controlling  the  discharges  of  the  chambers  and  hoppers,  electromagnets  dis- 
posed above  the  valves  and  adapted  when  energized  to  raise  the  same,  the  hoods 
and  deflectors  arranged  in  the  chambers  and  hopper  above  the  electromagnets, 
an  electrogenerator,  a  movable  commutator  and  circuit  wires  connecting  the 
magnets,  generator  and  commutator,  the  said  commutator  being  adapted  to  change 
the  circuits  and  the  condition  of  the  magnets. 

709593 — September  23,  1902.  D.  C.  BOLEY.  Apparatus  for  treating  pulverized 
ores  of  gold  and  silver. — The  difficulty  which  has  been  experienced  in  treating  finely 
divided  ores  by  filtration  with  a  cyanide  solution  is  well  known.  In  the  case  of 
battery  slimes,  which  are  produced  by  crushing  the  ore  in  the  battery  in  the  pres- 
ence of  either  water  or  a  cyanide  solution,  and  equally  in  the  case  of  the  fine  dust 
which  is  produced  by  dry  crushing  and  which  becomes  a  slime  by  the  addition 
of  moisture,  the  difficulty  in  all  these  arises  when  attempt  is  made  to  filter  the 
material,  so  as  to  draw  off  the  moisture,  because  the  slimes  collect  upon  the  sur- 
face  of  the  filter,  and  when  this  collection  reaches  a  certain  thickness  the  fluid 
will  no  longer  pass  through  and  the  filtering  surface  must  then  be  cleaned,  and 
this  difficulty  begins  very  soon  and  constantly  increases  as  the  filtering  "proceeds. 
Attempt  has  been  made  to  overcome  this  to  some  extent  by  producing  a  vacuum 
at  the  delivery  side  of  the  filter,  and  also  an  attempt  to  facilitate  the  filtration 
by  creating  an  air  pressure  on  the  other  side  of  the  filter;  and  it  has  been  attempted 
to  prevent  the  collection  of  this  impervious  coating  of  filtrates  by  stirring  and 
agitating  the  contents  of  the  filter.  So  far  there  has  been  no  organized  apparatus 
capable  of  carrying  on  this  work  of  filtering  slimes  successfully  and  economically, 
and  such  an  organized  apparatus  is  the  object  of  the  present  invention,  which 
consists  in  a  revolving  filter  cylinder  having  vacuum  chambers  and  means  for 
supplying  air  pressure,  the  filtering  surface  being  arranged  in  cylindrical  form 
inside  of  the  vacuum  chambers,  and  the  mode  of  operation  being  to  agitate  the 
pulverized  ore  by  revolving  the  cylinder  and  by  the  pressure  of  compressed  air, 
and  dissolving  the  gold  and  the  silver  in  the  presence  of  a  solution  of  potassium 
cyanide  and  of  the  oxygen  derived  from  the  compressed  air,  and  the  removal  of 
the  solution  containing  the  gold  and  silver  by  filtration,  assisted  by  the  vacuum, 
and  the  continuous  removal  of  the  filtrates  from  the  surface  of  the  filter  by  their 
own  gravity  in  the  turning  of  the  cylinder,  and  the  further  cleaning  of  the  filter 
surface  by  a  backward  blast  of  compressed  air  applied  after  the  filtering  there- 
through ceases. 

710462 — October  7,  1902.     R.  D.  JACKSON.     Settling-tank. — In  a  settling-tank, 
a  distributer  having  downwardly  extending  discharge  outlets  for  pulp  and  liquid,     <?>6 
means  for  supplying  material  to  said  distributer,  means  for  rotating  said  distributer, 
and  means  for  raising  said  distributer  while  rotating,  whereby  the  distributer 
rises  steadily  above  the  accumulating  deposit. 

710495— October  7,  1902.  S.  T.  MUFFLY.  Apparatus  for  treating  ores. — An 
apparatus  for  treating  ores,  comprising  a  rotary  cylinder,  air-inlet  and  outlet  pipes 
connected  therewith  at  opposite  ends  thereof,  automatic  valves  oppositely  directed 
and  controlling  the  inlet  and  outlet  pipes,  means  for  forcing  air  through  the  said 
inlet  pipe,  means  for  heating  the  said  air,  a  solvent  container  connected  with  the 
air-inlet  pipe  whereby  the  solvent  is  forced  by  and  with  the  air  into  the  rotary 
cylinder  in  the  form  of  a  spray,  means  for  governing  the  amount  and  pressure  of 
air  and  of  the  solvent,  devices  within  the  cylinder  for  scattering  and  agitating 
the  ores  as  the  said  cylinder  is  revolved. 

711236 — October  14,  1902.  H.  SMITH  and  P.  C.  BROWN.  Apparatus  for  use 
in  extracting  precious  metals  from  their  ores. — In  a  lixiviation  apparatus,  a  revoluble- 


368  APPENDIX 

tank,  pipes  conducting  a  solvent  air,  and  steam  to  the  tank,  means  for  rotating 
the  tank,  and  a  pipe  in  the  end  of  the  tank  opposite  the  end  containing  the  supply- 
pipe. 

712963 — November  4,  1902.  J.  J.  PRINDLE.  Barrel-filter. — In  a  chlorination 
barrel-filter,  a  platform  comprising  a  series  of  perforated  members  or  sections 
having  the  end  portions  thereof  thickened  or  enlarged,  said  enlarged  portions 
provided  on  their  lower  sides  with  prolonged  curved  faces  forming  supporting 
heels  which  conform  to  the  curvature  of  the  barrel  in  which  the  filter-platform 
is  adapted  to  be  used,  and  bolts  passing  through  said  curved  heels  and  co-operating 
therewith  in  holding  the  platform  in  place. 

713694 — November  18,  1902  J.  P.  SCHUCH,  Jr.  Ore-mixing-machine. — An  ore- 
mixing-machine,  comprising  the  following  elements:  An  ore-mixing-tank,  a  false 
bottom  including  a  strainer,  means  for  discharging  air  beneath  the  strainer  to 
keep  the  meshes  thereof  free  from  any  accumulation  of  slime  or  the  like,  air  supply- 
pipes  disposed  above  the  strainer  to  effect  aeration  of  the  contents  of  the  tank, 
a  track  carried  by  the  upper  outer  portion  of  the  tank,  an  agitator-shaft  having 
its  upper  portion  polygonal  in  cross-section,  a  spider  having  a  hub  engaging  the 
said  polygonal  portion  and  carrying  traveler-wheels  at  its  extremities  to  engage 
'the  track,  agitator-bars  suspended  from  the  spider,  and  beaters  or  stirrers  carried 
by  the  bars,  each  set  of  beaters  being  disposed  in  break-joint  order  with  relation 
to  the  adjacent  set  of  beaters. 

714822— December  2,  1902.  J.  RANDALL.  Settling-tank  or  decanting  vessel. — A 
settling-tank,  consisting  of  a  body  having  a  vertical  side  and  a  bottom  formed 
of  slopes  of  different  inclinations  and  provided  with  a  central  outlet,  the  said  side 
having  a  cutaway  portion  forming  an  overflow  lip,  a  launder  encircling  said  lip 
and  provided  with  a  discharge-spout,  a  baffle-plate  of  cylindrical  form  connected 
by  strips  to  the  upper  portion  of  said  side  and  extending  into  the  tank  below  the 
top  and  nearly  to  the  lower  edge  of  said  side,  and  a  pipe  leading  from  said  central 
outlet. 

718680 — January  20,'  1903.  B.  TULLY.  Barrel-filter. — A  filter,  comprising  a 
rotatable  barrel,  provided  with  a  lead  lining,  the  body  of  the  barrel  being  pro- 
vided with  apertures  and  the  lining  being  perforated  opposite  said  apertures,  a 
lead  launder  arranged  on  the  exterior  of  the  barrel  and  provided  with  a  plurality 
of  lead  branch  pipes,  said  branch  pipes  at  their  inner  ends  being  fitted  in  said  aper- 
tures and  connected  to  the  lead  lining  about  said  perforations. 

719273 — January  27,  1903.  Z.  B.  STUART.  Apparatus  for  treating  ores. — A 
tank  having  an  open  top  and  a  concave  bottom  formed  of  .perforated  removable 
plates,  a  removable,  conical  plate  upwardly  projecting  from  the  center  of  the  bot- 
tom, a  perforated  box  under  said  conical  plate,  a  layer  of  coarse  fabric  surround- 
ing said  perforated  box,  a  filtering  material  under  said  perforated  plates,  a  pump, 
a  suction-pipe  extending  from  said  pump  to  and  through  the  mixture  in  said  tank 
to  a  point  adjacent  to  the  upper  surface  of  the  mixture,  and  a  discharge -pipe  extend- 
ing from  said  pump  to  a  point  adjacent  to  the  conical  part  in  said  tank,  a  vacuum- 
tank,  a  pipe  connecting  said  vacuum-tank  to  said  perforated  box,  and  a  suction- 
pump  connected  to  said  vacuum-tank. 

719664 — February  3,  1903.  J.  B.  HEFFERNAN.  Chlorination  barrel — In  a 
chlorination  barrel  a  parallel  series  of  pipes  having  numerous  small  orifices  through 
their  longitudinal  walls,  one  or  more  headers  adapted  to  receiving  the  ends  of 
said  pipes,  a  valve  or  valves  connecting  said  header  or  headers  with  an  outside 
source  of  fluid  pressure. 

719756 — February  3,  1903.  S.  C.  C.  CURRIE.  Mechanism  for  mixing  and  stor- 
ing liquids  and  gases  for  ore  treatment. — In  combination,  an  alkali  mixing-tank, 
an  alkali  stock-tank  at  a  lower  level  and  connected  by  a  pipe  thereto,  a  mixing- 
chamber  at  a  level  below  the  alkaline  storage-tank,  safd  mixing-chamber  having 
inclines  leading  from  opposite  sides,  a  chlorine  gas  supply-pipe  leading  from  above 
the  top  of  the  mixing-chamber  into  the  bottom  thereof,  a  storage-tank  for  chlor- 
inated liquid  below  the  level  of  the  mixing-tank,  and  a  gas  supply-pipe  leading 
from  the  top  of  the  mixing-chamber  nearly  to  the  bottom  of  the  storage-tank. 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  369 

722314 — March  10,  1903.  L.  H.  MITCHELL.  -Discharge  means  for  tanks. — A 
discharge  apparatus  for  tanks,  provided  with  a  casting  having  an  upwardly  pro- 
jecting rim  provided  with  shoulders  having  longitudinally  inclined  under  faces, 
a  funnel  having  a  base  provided  with  a  depending  offset  portion,  a  gasket  mounted 
in  the  recess  formed  by  said  offset  portion  and  adapted  to  seat  upon  the  top  of 
the  rim,  lugs  formed  on  the  depending  portion  and  provided  with  longitudinally 
curved  upper  faces  to  engage  the  inclined  faces  of  the  shoulders,  and  operating 
handles  at  the  top  of  the  funnel. 

722399— March  10,  1903.  H.  R.  CASSEL.  Barrel-filter —A  barrel-filter  com- 
posed  of  a  barrel  having  a  lead  lining,  and  of  a  filter  having  rigid  cores  and  sur- 
rounding  lead  casings  made  integral  with  the  lining. 

7255Jt9 — April  14,  1903.      H.  R.  ELLIS.     Centrifugal  lixiviating-machine. — In  a 
centrifugal  filtering-machine,  the  combination  of  a  rotary-shaft,  a  drum  mounted 
thereon,  a  perforated  partition  within   the   drum,  arranged   concentrically  with 
the  periphery  of  the  drum  at  such  distance  therefrom  as  to  form  an  annular  chamber       <y 
about  the  perforated  partition,  means  for  supplying  liquid  to  the  annular  chamber,     V>< 
a  discharge  opening  in  the  bottom  of  the  drum,  a  cover  therefor  adapted  to  be 
held  open  by  centrifugal  force  when  the  drum  is  rapidly  rotated  to  permit  dis- 
charge of  the  charged  liquid,  and  to  be  held  in  closed  position  when  the  drum  is 
rotated  slowly,  and  a  discharge-gate  in  the  bottom  of  the  drum  at  a  point  nearer 
the  center  than  the  discharge  opening. 

727230—  Maij  5,  1903.  F.  G.  UNDERWOOD.  Leaching-tank  filter. — The  appa- 
ratus consists  of  a  tank  having  a  central  discharge  aperture  provided  with  a  mov- 
able closure,  an  interior  filter  diaphragm  spaced  from  the  bottom  of  the  tank  and 
having  a  central  discharge  aperture  registering  with  the  tank-discharge  aperture 
and  provided  with  a  movable  closure,  in  combination  with  vertical  filter  members 
radially  disposed  and  spaced  apart  between  said  discharge  apertures  and  the  walls 
of  the  tank  and  communicating  with  the  space  beneath  the  diaphragm. 

727362 — May  5,  1903.     H.  HIRSCHING.     Apparatus  for  treating  ores. — An  ore- 
treating  apparatus  including  a  leaching  vessel,  a  settler,  a  filter,  a  still,  a  condenser 
containing  a  coil,  a  stock-solution-tank,  and  an  absorption-tank,  said  absorption- 
tank  consisting  of  an  outer  casing  communicating  with   a  cooling-water-tank,  an      \, 
inner  casing  spaced  from  the  outer  casing  and  communicating  with  the  stock-  "Vv/ 
solution  tank,  and  an  innermost  casing  spaced  from  the  inner  casing  and  com-    < 
municating  with  the  coil  of  the  condenser,  whereby  the  vapors  and  fluid  emerging 
from  the  coil,  are  caused  to  flow  through  the  innermost  casing  and  through  the 
absorption  water,  and  the  absorption  water  is  caused  to  flow  through  the  inner 
casing  to  the  stock-solution-tank,  said  parts  being  connected  together  by  means 
of  pipes. 

728126 — May  12,  1903.  P.  W.  MCCAFFREY.  Precipitating  apparatus. — In  pre- 
cipitating apparatus,  the  combination  of  a  tank  having  curved  walls,  said  tank 
being  adapted  to  hold  the  solution  to  be  treated  and  being  provided  with  a  central 
partition  around  the  extremities  of  which  the  liquid  is  free  to  circulate,  blocks  or 
pieces  made  fast  to  the  opposite  sides  of  the  tank,  their  inner  surfaces  being  parallel 
with  the  surfaces  of  the  partition,  and  cylinders  mounted  to  rotate  on  opposite 
sides  of  the  partition  and  partially  immersed  in  the  solution,  said  cylinders  being 
perforated  and  containing  scrap  iron,  the  ends  of  the  cylinders  being  located  as 
cloee  to  the  partition  and  the  said  blocks  as  is  practicable  in  order  to  allow  perfect 
freedom  of  movement,  and  means  for  rotating  the  cylinders  in  reverse  directions 
whereby  the  .liquid  is  set  in  motion  in  a  circular  current. 

728746 — May  19,  1903.  P,  W.  MCCAFFREY.  Means  for  precipitating  dissolved 
metals. — In  precipitating  means,  the  combination  of  a  tank  adapted  to  hold  the 
liquor  from  which  the  precipitation  is  to  be  made,  a  number  of  perforated  cylinders 
containing  scrap  metal,  said  cylinders  being  mounted  to  rotate  in  said  tank  which 
is  constructed  to  receive  solution  at  one  end  and  discharge  it  at  the  opposite  end 
above  the  lowest  part  of  the  cylinders,  the  latter  being  arranged  in  successive 
order  from  the  feed  to  the  discharge  extremity  of  the  tank  and  partially  immersed 
in  the  solution,  and  suitable  means  for  producing  a  current  of  liquid  through  the 
tank  from  end  to  end,  whereby  the  contact  of  the  liquid  with  the  scrap  metal  in 
the  tanks  is  facilitated 


370  APPENDIX. 

729805 — June  2,  1903.  J.  STOVEKEN  and  L.  STOVEKEN.  Apparatus  for  ex- 
tracting metals  from  ores. — In  an  apparatus  for  extracting  precious  metals  from 
their  ores,  the  combination  of  a  tank  for  containing  a  cyanide  or  other  suitable 
solution,  means  for  reducing  ore  to  a  finely  divided  or  comminuted  state,  one  or 
more  conduits  connected  with  the  solution-tank  and  arranged  to  supply  the  ore 
with  solution  incident  to  the  reduction  thereof,  means  for  agitating  and  mixing 
the  ore  and  solution,  arranged  to  receive  the  same  from  the  reduction  means,  a 
filter  arranged  to  receive  the  ore  and  solution  from  the  agitating  and  mixing  means, 
and  adapted  to  separate  the  solution  from  the  ore,  one  or  more  decant  ing-tanks' 
arranged  to  receive  the  solution  or  solutions  from  the  filter,  a  precipitaling-tank 
which  receives  the  clear  solution  from  the  decanting-tank  or  tanks,  and  means  for 
transferring  the  solution  from  the  precipitating-tank  back  to  the  solution-tank. 

729806 — June  2,  1903.  J.  STOVEKEN  and  L.  STOVEKEN.  Agitation-tank. — 
The  combination  of  a  tank,  a  central,  vertical,  cylinder  arranged  therein,  a  piston 
movable  in  the  cylinder  and  having  a  rod  extending  through  the  upper  head  thereof, 
a  gear  disposed  above  the  tank  and  adapted  to  be  connected  by  a  driving  connec- 
tion with  a  motor,  a  shaft  stepped  on  the  piston-rod  and  keyed  to  and  adapted 
to  move  vertically  through  the  gear,  wings  connected  to  and  extending  inwardly 
from  the  vertical  wall  of  the  tank,  agitating  means  carried  by  the  said  shaft  and 
surrounding  the  upper  end  of  the  cylinder,  and  comprising  a  head  fixed  on  the 
shaft,  blades  disposed  below  the  wings  and  connected  together,  said  blades  being 
curved  in  the  direction  of  their  length  and  inclined  in  the  direction  of  their  width, 
connections  between  the  outer  portions  of  the  blades  and  the  head  of  the  shaft, 
connections  between  the  inner  portions  of  the  blades  and  said  shaft,  and  a  pipe 
communicating  with  the  cylinder  below  the  piston  and  adapted  to  be  connected 
with  a  source  of  fluid-pressure  supply. 

730195— June  2,  1903.  J.  STOVEKEN  and  L.  STOVEKEN.  Metallurgical  filter  — 
In  an  apparatus  for  extracting  precious  metals  from  their  ores,  the  combination 
of  a  filter  comprising  a  frame,  an  endless  filter-cloth,  means  for  driving  same,  means 
for  pressing  pulp  against  the  upper  stretch  of  the  cloth  at  different  points  and 
separate  receptacles  arranged  below  the  cloth  at  such  points,  and  a  decanting- 
vat  having  separate  tanks  connected  with  the  said  separate  receptacles  of  the 
filter;  the  said  separate  tanks  communicating  with  the  vat  at  their  upper  ends, 
and  having  valved  discharges  at  their  lower  ends. 

730384— June  9,  1903.  W,  H.  HOTTER,  Agitating  apparatus. — The  combina- 
tion of  a  rocking  platform,  means  for  operating  the  same,  a  frame  mounted  to 
reciprocate  adjacent  to  the  platform,  cylindrical  tanks  or  vats  trunnioned  on  the 
frame  and  engaging  the  platform,  flexible  devices  connected  with  the  opposite 
extremities  of  the  frame,  guides  therefor,  a  liquid  containing-tank,  a  piston  therein, 
stems  protruding  from  the  opposite  extremities  of  the  tank,  and  a  valve-controlled 
conduit  connecting  the  opposite  extremities  of  the  tank,  the  flexible  devices  of  the 
frame  being  connected  with  the  piston  stems. 

730385 — June  9,  1903.  P.  W.  MCCAFFREY.  Apparatus  for  the  precipitation  of 
metals  from  solutions. — In  apparatus  for  the  precipitation  of  dissolved  metallic 
values,  the  combination  of  a  tank  adapted  to  hold  the  solution  to  be  treated,  and 
a  perforated  receptacle  containing  scrap  metal,  the  perforated  walls  of  the  said 
receptacle  being  composed  entirely  of  the  same  material,  said  receptacle  being 
partially  immersed  in  said  solution  and  mounted  to  rotate  therein,  wherehv  the 
solution  is  mads  to  circulate  through  the  scrap  metal  for  the  purpose  set  forth. 

732720— July  7,  1903.  H.  DUNCAN  and  R.  R.  SHERRIFF.  Apparatus  for  sepa- 
rating liquids  from  solids. — A  machine  for  separating  liquids  from  solids,  com- 
prising in  combination  a  framing  and  gear,  carrying  and  traversing  an  endless 
band  of  filter-cloth,  automatic  slip  devices  for  securing  the  band,  a  vacuum-box 
or  suction-chamber  located  upon  the  under  surface  of  said  band,  and  an  interposed 
endless  band  of  wire  cloth  or  gauze  arranged  to  support  and  travel  with  the  filter- 
band. 

733739— July  14,  1903.  F.  H.  OFFICER,  R.  H.  OFFICER,  J.  H.  BURFEIND,  and 
J.  W.  NEIL.  Apparatus  for  use  in  metallurgical  processes. — In  an  apparatus  for 
treating  ores  or  other  materials  containing  gold  or  silver  or  other  metals  by  the 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.      371 

cyanide  process,  the  combination  of  a  treating-tank,  an  absorption-tank  containing 
a  caustic  solution,  a  compressor  and  connections  as  described  between  the  com- 
pressor, treating-tank  and  absorption-tank  whereby  air  or  gas  under  pressure 
may  be  forced  from  the  compressor  through  the  material  in  the  treating-tank  and 
tiie  gases  released  or  freed  from  said  material  may  be  passed  through  the  absorbing 
solution  in  the  regenerator-tank  and  thence  to  the  compressor,  so  as  to  permit 
the  air  to  be  used  over  and  over  and  the  valuable  products  released  in  the  treating- 
tank  to  be  recovered,  as  and  for  the  purpose  described. 

735206 — August  4,  1903.  L.  P.  BURROWS.  Mixing  and  dissolving  apparatus. 
— A  mixing  and  dissolving  apparatus,  comprising  a  containing  vessel,  a  shaft  in 
and  movable  relatively  to  said  vessel,  an  inner  and  an  outer  set  of  stirring-plates 
carried  by  and  arranged  around  and  substantially  parallel  to  said  shaft,  the  ad- 
jacent plates  of  the  inner  and  outer  sets  converging  toward  each  other  from  their 
front  to  their  rear  edges,  and  stirring-blades  secured  to  the  rear  edges  of  said 
plates  and  arranged  in  a  spiral  line  around  the  shaft,  the  corresponding  blades 
of  the  outer  and  inner  sets  being  twisted  in  opposite  directions. 

735834 — August  11,  1903.  L.  B.  SKINNER.  Filter. — A  filter-bar,  consisting  of 
a  body  portion  and  separated  tongues  projecting  laterally  therefrom  and  recessed 
for  the  passage  of  filtering  fluid,  each  tongue  with  a  beveled  end,  and  beveled  faces 
on  the  body  between  the  tongues. 

735835 — August  11,  1903.  L.  B.  SKINNER.  Filter. — The  combination  in  a 
filter-bed,  of  bars  having  each  a  body  portion  and  a  perforated  side  flange  with 
a  beveled  edge,  and  a  beveled  face  constituting  the  bearing  of  the  flange  of  the 
adjacent  bar. 

735960— August  11,  1903.  G.  S.  FOSTER  and  S.  S.  D.  STRINGER.  Metal-extract- 
ing and  ore-lixiviating  apparatus. — The  combination  of  a  solution-supply  tank, 
a  series  of  intercommunicating  leaching-tanks  adapted  to  receive  solution  from 
said  supply-tank,  drain-pipes  leading  from  said  leaching-tanks,  a  launder  into 
which  said  drain-pipes  are  arranged  to  discharge,  and  a  charcoal  box  connected 
to  said  launder, 

736036 — August  11,  1903.  H.  L.  SULMAN  and  H.  F.  KIRKPATRICK-PICARD. 
Apparatus  for  the  recovery  of  precious  metals. — In  an  apparatus  for  recovering 
precious  metals,  the  combination  of  a  conical  vessel  having  an  inner  amalgamated 
copper  surface,  a  conical  body  having  an  outer  amalgamated  copper  surface  dis- 
posed concentrically  within  the  vessel  and  forming  therewith  a  narrow  interspace, 
a  body  of  mercury  charged  with  an  electropositive  metal  in  the  interspace,  an 
electrolytic  vessel  for  charging  the  mercury,  a  mercury-pump,  an  inlet  conduit  to 
the  top  of  the  interspace  from  the  electrolytic  vessel,  an  outlet  conduit  for  mercury 
from  the  bottom  of  the  interspace  to  the  pump,  a  conduit  from  the  pump  to  the 
electrolytic  vessel,  an  inlet  conduit  at  the  bottom  of  the  vessel  for  the  solution 
carrying  the  values,  a  non-return  valve  in  said  conduit,  means  for  forcing  the 
solution  up  through  the  interspace,  and  a  launder  at  the  top  of  the  vessel  to  receive 
the  discharged  solution. 

736078— August  11,  1903.  H.  T.  DURANT.  Apparatus  for  the  treatment  cf  ores 
with  solvents. — A  device  for  the  treatment  of  ore,  tailings,  or  other  material  by 
solvents,  consisting  of  a  tank  having  a  conical  bottom,  a  plug  in  said  bottom  and 
made  conical  to  correspond  to  the  angular  walls  thereof,  a  pump  or  forcing  device 
discharging  into  the  apex  of  the  cone,  and  a  return  connection  between  the  upper- 
part  of  the  tank  and  the  suction  of  the  pipe. 

736597— August  18,  1903.  C.  D.  GROVE.  Barrel-filter. —In  a  barrel-strainer,, 
the  combination  with  the  shell  thereof  of  a  strainer  the  exterior  surface  of 
which^  is  in  contact  with  the  barrel,  its  inner  surface  being  provided  with  suitable 
straining  perforations  in  the  form  of  slits  combined  with  transverse  grooves  beneath 
the  interior  surface  and  establishing  communication  between  said  slits  and  the: 
discharge  opening. 

737046— August  25,  1903.  J.  B.  TRUITT,  W.  L.  TRUITT,  and  W.  O.  TEMPLE.. 
Precipitating  zinc  box. — In  a  precipitating;  zinc  box,  the  combination  of  an  outer 
imperforate  box  having  a  valved  outlet  in  its  bottom  and  a  valved  outlet  above 


372  APPENDIX. 

its  bottom,  a  launder  at  each  outlet,  and  an  inner  removable  zinc-holding  box 
having  a  perforated  bottom,  and  supported  in  the  outer  box  above  the  bottom 
of  the  latter. 

737533 — August  25,  1903.  E.  L.  V.  NAILLEN.  Apparatus  for  extracting  gold 
and  other  metals  from  ores. — In  an  apparatus  for  extracting  metals  from  ores,  the 
combination  of  a  concentrating-tank  consisting  of  two  cone-shaped  sections  secured 
together  at  their  largest  diameter  by  means  of  suitable  flanges  and  provided  with 
an  intermediate  strip  secured  between  said  flanges  and  projecting  outwardly, 
a  settling-tank  disposed  around  the  concentrating-tank,  a  perforated  diaphragm 
placed  between  the  concentrating-  and  settling-tanks  and  supported  upon  said 
intermediate  strip,  and  a  suitable  bracket  bolted  to  the  settling-tank  and  adapted 
to  form  two  horizontal  sections  within  the  settling-tank. 

738148 — September  8,  1903.  J.  B.  DE  ALZUGARAY  and  W.  A.  MERCER.  Appa- 
ratus for  extraction  of  precious  metals  from  their  ores. — Apparatus  for  treating  ores, 
consisting  of  a  closed  containing  vessel  or  vat  provided  with  fixed  internal  blades 
or  wings,  a  rotating  hollow  spindle  provided  with  ball-bearings  and  having  hollow 
blades  or  beaters  set  at  an  angle,  means  for  raising  and  lowering  the  spindle  in 
the  vat,  gearing  for  rotating  the  spindle,  and  means  connected  with  the  vat  for 
supporting  the  gearing  and  steadying  the  spindle,  all  combined,  arranged,  and 
operating  as  shown  and  described  and  for  the  purpose  set  forth. 

738329 — September  8,  1903.  W.  E.  HOLDERMAN.  Device  for  treating  slimes. — 
In  a  device  for  treating  slimes  having  a  liquid-tight  case,  a  discharge-pipe  pro- 
vided with  a  valve  in  its  bottom,  an  inclined  floor  in  said  case,  spaced  bars  on 
said  floor  and  the  sides  of  the  case,  a  filtering  fabric  covering  said  bars  and  over- 
lapping the  upper  edge  of  the  tank,  a  molding  to  hold  the  fabric  in  operative  posi- 
tion, and  pipes  provided  with  stoppers  leading  from  the  filter  out  through  said 
case. 

740193 — September  29,  1903.  E.  D.  SLOAN.  Barrel-filter. — In  a  barrel-filter", 
the  combination  with  the  barrel  of  a  partial  lining  of  porous  filter-blocks  fitting 
closely  together  and  having  grooves  formed  on  their  under  sides  which  intercon- 
nect from  block  to  block  and  form  drain  channels;  means  for  sealing  said  draining 
channels  from  the  inner  space  of  the  barrel,  and  a  discharge  port  leading  from 
the  drains  out  of  the  barrel. 

74.1189 — October  13,  1903.  H.  H.  THOMPSON.  Apparatus  for  extracting  precious 
metals. — An  apparatus  for  extracting  precious  metals,  comprising  a  receptacle 
provided  with  an  outlet,  a  series  of  bodily  movable  and  loosely  mounted  agitating 
.arms  gradually  decreasing  in  length  and  adapted  to  be  retained  in  their  operative 
position  when  rotated  in  one  direction  and  to  assume  an  inoperative  position  when 
moved  in  an  opposite  direction,  a  rotatable  means  for  suspending  said  arms  within 
said  receptacle,  said  rotatable  means  and  arms  bodily  movable,  a  series  of  screened 
nozzles  communicating  with  said  receptacle,  means  for  supplying  a  cyanide  solu- 
tion, compressed  air  and  water  to  each  of  said  nozzles  either  separately  or  in  any 
preferred  combination,  operating  means  for  said  rotatable  means,  and  means 
communicating  with  said  supply  means  and  the  said  outlet  for  exhausting  the 
solution  from  said  receptacle. 

741402 — October  13,  1903.  W.  E.  HOLDERMAN.  Leaching-tank. — In  a  filtering- 
tank  having  vertical  slats  covered  with  a  filtering  fabric,  a  filtering  partition  extended 
across  said  tank,  a  trough  in  its  bottom  for  the  filtrate,  and  an  orifice  through 
the  filtering  fabric  of  said  tank  into  which  the  filtrate  from  said  trough  is  dis- 
charged. 

741499 — October  13,  1903.  A.  E.  JOHNSON.  Barrel-filter. — In  a  barrel-filter, 
the  combination  with  a  suitable  barrel  or  cylinder,  of  a  filter  having  a  perforated 
bottom,  side  walls  extending  below  the  bottom  and  engaging  the  barrel  on  the 
inside,  filtering  material  resting  on  the  bottom  and  confined  by  the  side  walls,  a 
top  perforated  plate,  and  suitable  means  for  securing  the  filter  in  place,  a  channel 
being  formed  underneath  the  bottom  of  the  filter  to  receive  the  filtered  liquid, 
the  barrel  being  provided  with  a  valved  outlet  in  communication  with  the  said 
channel. 


PATENTS   RELATING  TO  CYANIDE  PROCESSES.  373 

743550 — November  10,  1903.  J.  A.  OGDEN.  Process  of  extracting  metals  from 
cyanide  solutions. — The  process  of  treating  gold,  silver,  or  other  metals  from  a 
cyanide  or  primary  solution,  consisting  in  mixing  in  a  receptacle  a  given  quantity 
of  said  primary  solution  with  a  given  quantity  of  a  secondary  solution  having 
a  metal  base  and  capable  of  liberating  the  metals  in  said  primary  solution;  leaving 
said  mixture  in  said  vessel  until  said  liberation  is  partially  effected,  then  passing 
said  mixture  into  a  second  receptacle  and  agitated  therein  so  as  to  produce  a  com- 
plete  commingling  of  said  solutions,  from  thence  running  the  mixed  solution  into 
a  settling-tank  and  allowing  it  to  settle,  drawing  off  the  clear  solution,  and  then 
drying  the  precipitation  and  pressing  and  melting  it  into  bullion. 

743551 — November  10,  1903.  J.  A.  OGDEN.  Apparatus  for  extracting  precious 
metals  from  cyanide  solutions. — An  apparatus  for  the  purpose  set  forth,  consisting 
of  primary  and  secondary  solution-tanks,  each  provided  with  discharge-pipes  with 
controlling-cocks,  and  measuring-glasses;  a  mixing  vessel  adapted  to  receive  the 
flow  from  said  measuring-glasses;  a  barrel  with  rotatable  blades  therein  and 
having  a  glass  gauge  on  the  outer  face  thereof,  and  a  settling-tank  adapted  to 
receive  the  discharge  from  said  barrel. 

745472— December  1,  1903.  W.  H.  ADAMS,  Jr.  Apparatus  for  treating  ores. — 
The  combination  of  a  tank,  a  box,  a  pipe  at  the  top  of  the  tank  connecting  the 
same  with  the  box,  a  pump  connected  with  the  box,  and  nozzles  connected  with 
the  pump  and  arranged  to  discharge  liquid  into  the  tank  at  intervals  tangen- 
tially  in  an  approximately  horizontal  plane. 

746867 — December  15,  1903.  DE  W.  C.  MOSHER.  Chlorination  barrel— A 
chlorinating  barrel  provided  with  a  resistant  lining  and  with  an  arched  channeled 
rib  extending  longitudinally,  secured  to  said  lining  and  having  perforations  between 
the  interior -of  the  rib  and  barrel,  and  a  discharge  opening  communicating  with 
the  interior  of  the  rib. 

748088 — December  29,^  1903.  G.  MOORE.  Filtering  system. — In  a  filtering  sys- 
tem, the  combination  with  a  tank  for  containing  the  material  to  be  filtered  and 
a  cleansing-fluid  tank,  of  a  filter,  means  for  introducing  and  removing  the  same 
into  and  from  each  of  said  tanks  alternately,  means  for  drawing  the  contents  of 
said  tanks  through  the  filter,  and  means  for  cleansing  the  filter. 

748217 — December  29,  1903.  C.  H.  RIDER.  Apparatus  for  dissolving  organic  or 
inorganic  substances. — A  device  consisting  of  an  acid-tank,  a  water-tank,  an  upper 
series  of  tanks  connected  with  the  acid-tank  and  the  water-tank  and  to  each  other, 
a  lower  series  of  tanks  adapted  to  receive  the  substance  to  be  treated,  connected 
to  the  upper  series  of  tanks  and  to  the  water-tank  and  to  each  other;  a  retort, 
means  for  heating  the  retort,  a  pipe  passing  from  the  retort  through  the  lower 
series  of  tanks,  and  a  condenser  into  which  the  last-named  pipe  extends,  substan- 
tially as  and  for  the  purposes  specified. 

748462— December  29,  1903.  W.  J.  ARMBRUSTER.  Chlorination  barrel. — A 
chlorination  barrel  having  a  pulp-chamber  and  a  chlorine  generating  compart- 
ment rotatable  therewith,  a  wall  separating  the  pulp-chamber  from  the  compart- 
ment, said  wall  having  an  unobstructed  opening  disposed  about  the  axis  of  rota- 
tion of  the  barrel  for  freely  permitting  the  discharge  of  the  chlorine  above  the 
surface  of  the  pulp  in  the  pulp-chamber. 

/ 

CLASS  75— METALLURGY. 

SUBCLASS  185 — CYANIDES. 

323222— July  28,  1885.  J.  W.  SIMPSON.  Process  of  extracting  gold,  silver, 
and  copper  from  their  ores. — The  ore  is  crushed  to  a  powder,  treated  with  a  solu- 
tion produced  by  dissolving  1  pound  of  cyanide  of  potassium,  1  ounce  of  carbon- 
ate of  ammonia,  and  £  ounce  of  chloride  of  sodium  in  16  quarts  of  water  when 
the  ore  contains  gold  and  copper  only;  but  when  it  is  rich  in  silver  the  quantity 
of  chloride  of  sodium  employed  is  increased.  After  thorough  agitation  of  the 
ore  in  the  solution  the  mixture  is  allowed  to  stand  until  the  solution  has  become 


374  APPENDIX. 

clear,  when  the  dissolved  metals  are  precipitated  out  by  means  of  a  plate  of  zinc 
suspended  in  the  liquid.  The  metal  is  precipitated  upon  the  zinc  and  can  be 
removed  by  scraping  or  by  dissolving  the  zinc  in  sulphuric  or  hydrochloric  acid. 

403202 — May  14, 1889.  J.  S.  MACARTHUR,  R.  W.  and  WM.  FORREST.  Process 
of  obtaining  gold  and  silver  from  ores. — The  invention  consists  in  subjecting 
finely-powdered  argentiferous  ores  to  the  action  of  a  solution  containing  a  small 
quantity  of  a  cyanide,  the  cyanide  contents  of  the  latter  being  proportioned  to 
the  quantity  of  gold  or  silver,  or  both,  found,  by  assaying  or  otherwise,  to  be  in 
the  ore.  Any  cyanide  soluble  in  water  may  be  used,  but  in  all  cases  the  solution 
must  be  extremely  dilute,  since  such  a  solution  has  a  selective  action  in  dissolving 
gold  or  silver  in  preference  to  the  baser  metals.  The  claim  covers  the  use  "  of  a 
cyanide  solution  containing  cyanogen  in  the  proportion  not  exceeding  8  parts 
of  cyanogen  to  1000  parts  of  water." 

41 8 137 —December  24,  1889.  J.  S.  MACARTHUR,  R.  W.  and  WM.  FORREST. 
Process  of  separating  gold  and  silver  from  ore. — This  invention  has  for  its  object 
the  preventing  of  loss  of  cyanide  in  the  care  of  weathered  ores  by  first  neutraliz- 
ing the  ore  with  an  alkali  or  alkaline  earth  and  then  leaching  such  prepared  charge 
with  a  cyanide  solution.  Further,  the  precious  metal  thus  dissolved  in  the  cyanide 
solution  is  precipitated  out  by  passage  through  a  sponge  of  zinc  composed 
of  fine  threads  or  filaments  of  zinc  formed  by  cutting  shavings  with  a  turning  tool 
from  a  series  of  zinc  disks  held  in  a  lathe,  or  by  passing  molten  zinc  at  a  tempera- 
ture just  above  the  melting-point  through  a  fine  sieve  and  allowing  it  to  fall  into 
water. 

482577— September  13,  1892.  E.  D.  KENDALL.  Composition  of  matter  for  the 
extraction  of  gold  and  silver  from  ores. — Consists  in  extracting  gold  and  silver  from 
minerals,  "  tailings,"  and  other  matters  containing  one  or  both  of  these  metals 
by  an  aqueous  solution  of  one  or  more  soluble  ferricyanides  and  one  or  more  soluble 
cyanides  prepared  by  dissolving  a  ferrocyanide  in  one  portion  of  water  and  a  cyanide 
in  another  portion  and  mixing  the  two  solutions,  or  by  adding  either  salt  in  solid 
form  to  the  solution  of  the  other. 

492221 — February  21,  1893.  C.  MOLDENHAUER.  Extracting  gold  from  its  ores. — 
Consists  in  subjecting  gold  ores  to  the  solvent  action  of  cyanide  of  potassium  in 
the  presence  of  ferricyanide  of  potassium. 

494054 — March  21,  1893.  W.  A.  G.  BIRKIN,  Process  of  and  solvent  for  sepa- 
rating precious  metals  from  their  ores. — Covers  the  art  of  separating  metals  from 
their  ores  by  subjecting  the  suitable  comminuted  ore  to  the  action  of  a  menstruum 
composed  of  potassium  cyanide,  potassium  ferricyanide,  and  peroxide  of  hydrogen 
in  water,  and  separating  the  values  from  this  solution  by  precipitation,  deposition, 
or  electrolysis. 

496950 — May  9, 1893.  H.  PARKES  and  J.  C.  MONTGOMERIE.  Process  of  extract- 
ing gold  or  silver.— Claims  a  process  for  extracting  gold  and  silver  from  ores  or 
compounds  by  an  interrupted  operation,  consisting  of  treating  the  ore  with  cyanide 
of  potassium  in  the  presence  of  oxygen  under  pressure  with  agitation,  the  ore 
being  subsequently  filtered  and  washed  and  the  precious  metals  recovered  from 
the  liquor  by  precipitation  or  other  known  means. 

514^57 — February  6,  1894-  W.  P.  MILLER.  Process  of  recovering  precious 
metals. — Has  for  its  object  the  preservation  of  the  cyanide  solution,  and  consists 
in  the  treatment  of  the  ore  with  the  cyanide  solution  in  air-tight  vessels  not  only 
during  the  process  of  solution,  but  during  the  filtration  and  up  to' the  time  of  the 
precipitation  of  the  precious  metals  from  the  filtered  solution. 

622739 — July  10,  1894.  C.  MOLDENHAUER.  Process  of  precipitating  gold  or 
other  precious  metals  from  their  solutions — Dissolves  gold  and  other  precious  metals 
from  their  ores  by  means  of  acid-cyanide  solutions,  which  consist  in  treating  the 
solution  with  aluminum,  so  as  to  precipitate  the  gold  from  the  solution,  and  then 
add  a  free  alkali  or  alkaline  earth  for  a  regenerating  solution. 

524601 — August  14,  1894.  J-  C.  MONTGOMERIE.  Process  of  extracting  gold 
or  silver  from  ores. — Sodium  oxide  (caustic  soda)  or  other  suitable  oxide  of  the 
alkalies  is  added  to  the  cyanide  solution  before  mixing  the  same  with  the  ore. 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  375 

After  the  precious  metals  have  been  dissolved  in  the  solution  and  the  liquid  filtered 
off  and  the  precious  metals  precipitated  out,  the  remaining  solution  is  tested  to 
determine  the  quantities  of  potassium  and  sodium  oxide  still  remaining  in  it,  and 
any  deficiency  is  supplied  or  the  solution  fortified  by  the  addition  of  the  necessary 
quantity  of  these  agents,  so  as  to  restore  the  solvent  solution  to  its  original  char- 
acter and  strength. 

524690 — August  14,  1894,  E.  D.  KENDALL.  Method  of  treating  gold  or  silver 
ores. — Covers  the  treating  of  gold  or  silver  ores  with  a  composition  of  matter  con- 
sisting of  sodium  dioxide  and  a  suitable  cyanide  in  solution.  /  • 

532238 — January  8,  1895.     C.  MOLEENHAUER.     Method  of  precipitating  precious    '  * 
metals  from  solutions.— Consists  in  subjecting  the  ores  to  the  action  of  an  acid-   ^  *j 
cyanide  solution  so  as  to  dissolve  the  gold  or  other  precious  metal"  contained  in   J 
them,  then  adding  aluminum  so  as  to  precipitate  the  gold  or  other  metal  from 
the  solution,  and  then  regenerating  the  cyanide  solution  by  means  of  a  free  alkali 
or  alkaline  earth. 

532895 — January  22,  1895.  J.  C.  MONTGOMERIE.  Process  of  extracting  gold 
or  silver  from  ores.— Consists  in  adding  an  oxide  or  one  of  the  alkaline  bases  to  a 
cyanide  solution,  then  mixing  with  the  ore  or  compound  the  solution  thus  rendered 
alkaline,  then  conducting  the  process  under  pressure  of  oxygen,  and  afterwards 
separating  from  the  ore  the  liquid  containing  the  gold  and  silver  in  solution,  then 
treating  that  liquid  in  any  approved  way  for  the  recovery  of  the  precious  metal, 

538951 — May  7,  1895.  S.  C.  CLARK.  Process  of  treating  refractory  ores. — Claims 
the  process  of  treating  a  refractory  ore,  consisting  essentially  in  boiling  the  ore  I 
in  water  containing  from  10  to  15  pounds  of  cyanide  of  potassium  to  each  ton 
of  ore  for  about  one  hour  or  for  a  sufficient  length  of  time  to  enable  the  cyanide 
of  potassium  to  dissolve  the  chloride,  sulphide,  or  bromide  in  the  ore,  then  allow- 
ing the  solution  to  settle  and  finally  evaporating  the  clear  liquid  so  as  to  obtain; 
a  residue  containing  metal. 

540359 — June  4)  1895.  G.  KENNAN.  Process  of  and  apparatus  for  treating 
ores. — Claims  the  process  of  treating  the  ores  of  gold  and  silver,  consisting  in  sub- 
jecting the  same  to  the  action  of  cyanide  of  potassium,  agitating  the  same  for  a 
short  period  of  time,  discontinuing  the  agitation,  and  bringing  air  in  contact  there- 
with, the  oxygen  thereof  increasing  the  action  of  the  cyanide,  continuing  the  agita- 
tion for  a  few  minutes,  until  every  particle  of  ore  has  been  brought  in  contact 
with  the  cyanide  solution  in  the  presence  of  atmospheric  air,  and  withdrawing 
the  solution  from  the  remaining  pulp  or  ore. 

541333 — June  18,  1895.     F.  RINDER.     Process  of  separating  gold  and  silver. — 
Consists  in  the  treatment  of  cyanide  solutions  containing  gold  and  silver  with    ^/ 
sulphide  of  iron  to  precipitate  the  silver  and  then  with  chloride  of  zinc  to  pre-    /\. 
cipitate  the  gold. 

543543 — July   80,   1895.     M.    E.    WALDSTEIN.     Process   of   extracting  gold   or 
silver  from  ores. — Consists  in  subjecting  the  ores  to  the  action  of  cyanide  of  potas-  » 
shim,  adding  to  the  material  during  this  action  a  salt  or  salts  (such  as  bin  oxide  1 
of  barium)  decomposable  by  an  acid  and  yielding  oxygen,  and  sufficient  acid  to   ' 
decompose  this  salt  or  salts,  and  subsequently  adding  an  excessive  acid  to  decom- 
pose the  soluble  cyanide  and  finally  separating  the  precious  metals  as  sulphides 
by  precipitation  with  sulphureted  hydrogen  or  by  a  soluble  sulphide. 

543782 — July  30,  1895.  M.  CRAWFORD.  Process  of  extracting  precious  metals 
from  their  ores,— Consists  first  in  lixiviating  the  ores  of  the  precious  metals  with  a 
cyanide  solution  to  which  has  been  added  a  substantially  neutral  substance  which 
contains  a  permanent  excess  of  oxygen;  second,  in  subjecting  the  gangue  and 
accompanying  cyanide  solution  to  an  amalgamating  process;  and,  thirdly,  in 
withdrawing  the  solution  from  the  tailings,  and  extracting  the  precious  metuls 
therefrom.  The  neutral  substance  containing  a  permanent  excess  of  oxygen  may 
be  prepared  by  mixing  peroxide  of  sodium  with  dilute  sulphuric  acid  and  neu- 
tralizing with  silicate  of  soda. 

543676 — July  30,  1895,  M.  CRAWFORD.  Process  of  extracting  precious  metals 
from  their  ores. — Consists  in,  first,  lixiviating  the  ore  with  a  cyanide  solution  to 


376  APPENDIX. 

which  has  been  added  a  small  quantity  of  a  substance  prepared  by  agitating  ether 
with  binoxide  of  barium  and  adding  thereto  small  quantities  of  very  dilute  hyciro- 
•chloric  acid,  and  neutralizing  by  silicate  of  soda,  and,  second,  separating  the  precious 
.metal  fiom  this  solution  in  which  the  ore  has  been  lixiviated. 

545852 — September  8,  1895.  P.  DE  WILDE.  Method  of  extracting  gold. — The 
precipitation  of  gold  in  the  iorm  of  a  mixture  of  aurous  cyanide  and  cuprous  cyanide 
by  acidulating  a  cyanide  solution  containing  the  gold  with  an  acid  sulphurous 
•compound  and  afterwards  adding  a  solution  of  copper  salt.  Also,  specifications 
provide  for  the  dissolving  of  gold  by  the  use  of  a  weak  solution  of  potassium  or 
sodium  cyanide  which  has  been  in  contact  with  the  minimum  or  protoxide  of  lead, 
and  for  the  recovery  and  utilization  of  the  spent  cyanide  by  its  conversion  to  Prus- 
sian blue. 

547790— -October  15,  1895.  J.  J.  HOOD.  Extracting  metals. — The  method  for 
the  extraction  of  precious  metals  from  their  ores,  which  consists  in  treating  the 
ore  with  a  solution  containing  both  a  cyanide  of  potassium  or  sodium  and  a  salt 
or  compound  of  a  baser  metal  in  the  proportion  of  one  part  at  least  of  the  former 
to  two  parts  of  the  latter;  the  metallic  base  of  the  solution  being  displaced  by 
the  precious  metal,  the  former  being  precipitated.  The  gold  is  then  precipitated 
out  by  a  copper-zinc  couple.  By  "  baser  metal  "  is  meant  mercury,  lead,  and 
such  other  metals  as  are  displaced  by  metallic  gold  from  their  solutions  in  alka- 
line cyanides  A  mixture  that  answers  well  consists  of  two  parts,  by  weight,  of 
cyanide  of  potassium  (or  its  equivalent  of  cyanide  of  sodium),  one  part  of  mer- 
curic chloride  or  its  equivalent  of  sulphate  or  other  mercury  salt,  and  from  one- 
half  to  two  parts  of  caustic  soda. 

549736 — November  12,  1895.  J,  C.  MONTGOMERIE.  Extraction  of  gold  and 
.silver  from  ores. — The  improved  process  of  extracting  gold  and  silver  from  ores 
or  compounds  containing  the  same,  consisting  in  treating  the  ore  in  a  vessel  con- 
taining water  with  a  cyanide,  an  alkaline  oxide,  a  nitrate,  and  an  oxidizing  agent. 
.Sodium  dioxide  may  be  taken  as  a  representative  of  the  alkaline  oxide  and  aid 
under  pressure  as  an  oxidizing  agent,  as  set  forth  in  this  claim. 

555463 — February  25,  1896. — J.  S.  MACARTHUR  and  C.  J,  ELLIS.  Process  of 
^extracting  gold  and  silver  from  ores: — Consists  in  subjecting  the  ore  to  the  action 
of  a  cyanide  solution  and  precipitating,  by  means  of  a  metallic  compound  capable 
of  combining  with  sulphur  any  sulphur  which  may  become  soluble  in  the  solution 
and  thereby  rendering  it  inert.  Salts  or  compounds  of  lead,  manganese,  zinc, 
mercury,  and  iron  are  types  of  the  metallic  compound  employed.  By  means 
of  a  salt  of  lead  any  copper  present  in  the  cyanide  solution  may  be  precipitated 
out. 

555483 — February  25,  1896.  T.  L.  WISWALL  and  J.  B.  FRANK.  Process  of 
recovering  precious  metals  from  solutions. — The  process  of  extracting  precious  metals 
from  solutions  by  causing  said  solutions  to  flow  through  a  precipitating  alloy, 
subdivided  into  a  mass  of  hardened  filaments,  and  composed  of  zinc,  lead,  and 
one  or  more  other  metals  which  impart  to  said  filaments  a  tensile  strength  suffi- 
cient to  withstand  the  compression  of  the  flowing  solution,  such  as  arsenic,  anti- 
mony, cadmium,  or  bismuth,  and  in  which  alloy  there  is  present  not  more  than 
97  per  cent,  of  zinc. 

576173 — February  2,  1897.  H.  L.  SULMAN.  Process  of  precipitating  precious 
metals  from  their  solutions. — Consists  in  purifying  zinc  fumes  or  dust  of  oxides 
by  intimately  mixing  with  the  same  an  ammoniacal  substance,  and  then  mixing 
a  quantity  of  said  fumes  or  dust  so  purified  with  the  solution.  The  apparatus 
by  which  to  perform  the  process  and  for  the  treatment  of  the  ores  is  also  claimed. 

578089 — March  2,  1897.  J.  F.  WEBB.  Process  of  extracting  gold  and  silver 
from  ores. — The  process  or  method  for  the  extraction  of  gold  and  silver  from  their 
crushed  ores,  consisting  in  saturating  the  ores  in  a  solvent  solution  of  potassium 
cyanide,  then  applying  a  current  of  compressed  air  from  beneath  and  maintaining 
the  same  throughout  the  leaching  process,  then  shutting  off  the  current,  then 
applying  a  current  of  compressed  air  on  top  of  the  solution  after  the  ore-contain- 
ing Vat  has  been  closed  at  top  and  a  drain  at  the  bottom  has  been  opened,  and 
maintaining  the  same  until  the  solution  has  been  driven  out  of  the  ore,  then  shut- 
.ting  off  the  current  of  air,  then  admitting  water  to  the  vat,  then  introducing  a 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  377" 

compressed-air  current  at  the  bottom  of  the  vat,  and  finally  introducing  a  cur- 
rent of  compressed  air  on  top  after  the  vat  has  been  again  closed  at  top  and  a- 
drain  opened  at  bottom. 

578178— March  2,  1897,  D.  WHITE  and  T.  M.  SIMPSON.  Process  of  and  appa- 
ratus for  extracting  precious  metals  from  slimes,  etc. — In  the  extracting  of  precious 
metals  from  slimes  and  other  auriierous  and  argentiferous  materials,  the  process 
which  consists  in  mixing  the  said  material  with  a  cyanide  solution  in  a  closed  vusel,. 
then  agitating  the  mixture  by  passing  a  gas  under  pressure  through  tLe  s.Lrr.e, 
then  passing  "gas  under  pressure,  together  with  the  gases  arising  from  tLe  acilon 
of  the  cyanide  solution  in  the  said  material,  through  another  quantity  oi  stud 
material  and  cyanide  solution  in  a  closed  vessel,  then  conveying  the  gases  Lack 
to  the  source  of  compression  and  drawing  off  the  solution,  containing  the  precious 
metal  and  extracting  said  metal.  The  apparatus  for  accomplishing  this  purpose 
is  also  claimed. 

578340 — March  9,  1897.  W.  A.  KONEMAN.  Process  of  extracting  precious 
metals  from  their  ores. — The  process  of  extracting  precious  metal  from  the  ore 
containing  it,  which  consists  in  wetting  the  ore,  in  a  pulverized  condition,  with 
just  sufficient  cyanogen-containing  solution  to  moisten  the  ore  and  reduce  the 
mass  to  the  condition  of  mud,  maintaining  the  saturated  ore  in  a  quiescent  state 
for  a  prolonged  period  of  time,  then  diluting  the  mass  and  subjecting  it  to  agita- 
tion for  a  suitable  period  of  time,  separating  the  resultant  solution  from  the  ore 
by  filtration,  and  finally  precipitating  the  precious  metal  from  said  solution. 

578341 — March  9,  1897.  W.  A.  KONEMAN.  Process  of  recovering  precious- 
metals  from  cyanide  solutions  containing  them. — The  process  of  recovering,  by  pre- 
cipitation, the  precious  metal  or  metals  contained  in  a  cyanogen-containing  solu- 
tion, which  consists  in  subjecting  said  solution  to  contact  with  an  alloy  composed 
of  load  and  zinc,  and  in  which  lead  is  the  preponderating  metal  in  weight,  or  with 
an  alloy  composed  of  lead,  zinc,  and  aluminv.m. 

580683 — April  13,  1897.  C.  W.  H.  GCPNER  and  H.  L.  DIEHL.  Recovery  of 
gold  and  silver  from  their  solutions. — The  process  for  the  precipitation  of  gold  and 
silver  from  their  cyanide  solutions,  which  consists  in  adding  to  Faid  solutions  a  ^Jf 
Considerable  quantity  of  cuprous  cyanide,  then  adding  an  acid  to  effect  precipi- 
tation, dissolving  the  latter  by  a  fresh  quantity  of  the  cyanide  solution  obtained 
by  leaching,  and  then  adding  acid  to  effect  successive  precipitations  from  said 
solution. 

580948 — April  20,  1897,  J.  C.  MONTGOMERIE.  Process  of  treating  cyanide  solu- 
tions.— The  process  for  the  extraction  of  the  precious  metals  from  cyanide  solu- 
tions, which  consists  in  filtering  the  solution  through  a  charcoal  filter,  heating 
the  filtering  material  on  the  same  becoming  surcharged  with  cyanogen  or  its  com- 
pounds, condensing  the  resultant  gases  and  obtaining  ammonium  cyanide  and  ^Q/ 
other  ammonium  salts  in  solution,  applying  the  regenerated  charcoal  (still  con- 
taining the  precious  metals)  in  the  filtration  of  a  further  charge  or  charges  of  the 
solution,  and  ultimately  recovering  from  the  charcoal  the  precious  metals  accu- 
mulated therein. 

587179 — July  27, 1897.     J  H.  BURFEIND.     Treatment  of  gold  and  silver  ores. — As 
an  improvement  in  the  extracting  of  precious  metals  from  their  ores,  the  treat—    -^N^ 
ment  of  the  cyanide  product  or  precipitate  containing  said  metals,  preparatory 
to  melting  the  said  product  with  sulphurous  acid. 

591753 — October  12,  1897.  E.  J.  FRASER.  Process  of  obtaining  precious  metals 
by  solution. — The  process  of  treating  gold  and  silver  ores  by  solution,  which  con- 
sists in  converting  the  metal  bases  of  dioxides  of  the  alkaline  metals  into  sulphates, 
by  the  addition  of  sulphuric  acid,  so  as  to  produce  hydrogen  dioxide,  preventing 
the  decomposition  of  the  hydrogen  dioxide  by  an  excess  of  acid,  separating  the 
solution  from  the  metallic  sulphate,  mixing  the  solution  with  a  solution  of  cj^anide 
of  potassium  and  lime  in  the  presence  of  a  precious  metal,  and  leaching  the  liquid 
holding  the  precious  metal. 

592153— October  19,  1897.  J.  S.  MACARTHUR.  Precipitating  precious  metals 
from  solutions. — The  process  of  precipitating  a  precious  metal  from  a  cyanide 
solution,  which  consists  in  subjecting  said  solution  containing  a  base  metal  to 
the  action  of  a  precipitant  protected  by  a  metal  inert  in  said  solution.  Such  a 


378  .  APPENDIX. 

precipitant  is  found  in  zinc,  mercury,  or  copper  protected  by  lead.  When  cop- 
per is  present  in  the  cyanide  solution,  this  copper  is  removed  by  the  precipitant 
prior  to  the  removal  of  the  precious  metal. 

601201 — March  22,  1898.  S.  NEWHOUSE,  A.  J.  BETTLES,  and  T.  WEIR.  Method 
or  process  of  extracting  precious  metals  from  their  ores. — A  method  or  process  for 
the  extraction  of  the  precious  metals  from  their  ores,  said  method  or  process  con- 
sisting, first,  in  neutralizing  the  acidity  of  the  ore  where  this  condition  exists; 
second,  in  placing  the  ore  in  a  suitable  solution  of  cyanide  of  potassium  and  sub- 
jecting the  mass  to  agitation;  third,  in  adding  a  quantity  of  zinc  to  the  mixture 
of  ore  and  cyanide  and  subjecting  the  mass  to  further  agitation;  and,  fourth,  in 
adding  quicksilver  or  mercury  charged  with  sodium  amalgam,  and  finally  agitating 
the  entire  mass  for  purposes  of  amalgamation. 

607719 — July  19,  1898.  M.  E.  WALDSTEIN.  Process  of  recovering  precious 
•metals  from  their  solutions. — The  process  for  extracting  and  recovering  precious 
metals  from  their  ores,  which  consists  essentially  of  the  following  steps:  First, 
subjecting  the  ore  in  a  powdered  state  to  the  action  of  an  aqueous  solution  of  a 
cyanide;  second,  supplying  to  the  solution  charged  with  the  precious  metals  that 
quantity  of  zinc  dust  determined  to  be  exactly  sufficient  to  precipitate  said  metals; 
third,  agitating  said  solution  and  said  zinc  dust  until  said  metals  are  precipitated 
and  said  zinc  dust  is  absorbed;  fourth,  recovering  the  precious  metals  from  the 
valuable  precipitate  of  the  preceding  step  by  filtration,  or  other  process. 

610616— September  13,  1898.  H.  L.  SULMAN  and  F.  L.  TEED.  Extraction 
of  precious  metals  from  their  ores. — The  essence  of  this  invention  consists  in  the 
employment  of  haloid  compounds  of  cyanogen  in  combination  with  free  cyanide 
of  potassium  or  other  suitable  cyanide  of  the  alkalies  or  alkaline  earths  as  a  sol- 
vent for  precious  metals  in  their  ores,  examples  of  such  haloid  compounds  of  cyanogen 
being  found  in  cyanogen  chloride,  or  bromide  or  iodide. 

620100 — February  28,  1899.  W.  A.  CALDECOTT.  Method  of  extracting  gold 
from  cyanide. — An  improved  method  for  the  precipitation  of  gold  from  gold-bear- 
ing cyanide  solutions  by  passing  such  solutions  over  zinc  shavings  previously 
treated  with  a  soluble  salt  of  mercury,  such  as  perchloride  of  mercury  (HgCl2). 


) — May  2,  1899.  C.  B.  JACOBS.  Process  of  reducing  metals  from  their 
solutions'. — The  process  of  reducing  metals  from  their  solutions,  consisting  in  sub- 
jecting them  to  the  action  of  gaseous  phosphide  of  hydrogen  in  the  presence  of 
an  alkaline  material,  thereby  precipitating  the  noble  metals  in  a  metallic  state 
and  the  base  metals  as  phosphides,  and  then  separating  the  latter  from  the  noble 
metals. 

625564 — May  23,  1899,  E.  D.  KENDALL.  Process  of  treating  gold  or  silver 
ores  and  composition  of  matter  for  same  purpose. — A  composition  of  matter  to  be 
used  for  extracting  precious  metals  from  ores,  tailings,  or  other  bodies,  consisting 
of  a  suitable  thiocyanate  and  a  suitable  ferrocyanide  in  watery  solution. 

625565 — May  23,  1899.  E.  D.  KENDALL.  Process  of  treating  gold  or  silver 
ores  and  composition  of  matter  for  same  purpose. — A  composition  of  matter  to  be 
used  for  the  extraction  of  precious  metals  from  ores,  tailings,  or  other  bodies,  con- 
sisting of  a  suitable  thiocyanate  and  hydrogen  dioxide  in  watery  solution. 

629905 — August  1,  1899.  J.  J.  HOOD.  Process  of  extracting  gold  or  silver. —  The 
process  of  extracting  gold,  silver,  and  mercury  from  solutions  by  bringing  the 
solutions  into  contact  with  an  alloy  of  zinc,  antimony,  and  mercury,  from  time 
to  time  distilling  off  mercury  from  the  alloy,  and  finally  recovering  the  gold  and 
silver  from  it.  The  precipitant  used  consists  of  an  alloy  of  about  one  hundred 
parts  of  zinc,  five  parts  of  antimony,  and  twenty  parts  of  mercury. 

630982 — August  15,  1899.  W.  KEMMIS-BETTY  and  B.  SEARLE.  Process  of 
recovering  gold  from  pulp,  slimes,  or  similar  substances. — The  process  of  extracting 
gold  from  ores,  which  consists  of  the  following  steps:  First,  dissolving  the  gold 
m  the  pulp  in  a  weak  solution  of  cyanide  of  potassium:  second,  adding  a  stronger 
solution  of  cyanide  of  potassium  to  the  gold-bearing  solution  in  the  proportions 


PATENTS  RELATING  TO  CYANIDE   PROCESSES.  379 

specified;    third,   immediately   after  so  strengthening  the    solution,   passing  the 
same  through  a  body  of  zinc  shavings  coated  with  lead. 

635199 — October  17, ,1899.  J.  SMITH.  Process  of  treating  gold  or  silver  ores. — The 
process  for  treating  gold  and  silver  ores,  tailings,  slimes,  and  like  materials  con- 
taining precious  metals,  which  consists  in  mixing  the  material  to  be  treated  with 
caustic  lime,  saturating  or  covering  the  mixture  entirely  with  water  and  keeping 
it  thus  until  all  the  acid  present  has  combined  with  the  lime,  drying  the  material, 
exposing  it  to  the  action  of  atmospheric  air,  and  treating  it  with  a  cyanide. 

636114 — October  81,  1899.  J.  S.  CAIN,  A.  SODERLING,  and  S.  M.  MACKJNIGHT. 
Preliminary  treatment  of  ores  or  tailings  before  cyaniding. — The  method  or  process 
of  treating  ores  containing  the  precious  metals,  which  conissts  in  first  leaching 
said  ores  or  tailings  in  a  weak  solution  of  nitric  acid,  or  of  nitric  and  sulphuric 
acids,  subsequently  leaching  the  same  in  an  alkaline  solution,  and  finally  leaching 
the  same  in  a  cyanide  solution. 

636288 — November  7,  1899.  H.  DE  RAASLOFF.  Process  of  extracting  precious 
metals  from  ores. — The  improvement  in  the  process  of  separating  precious  metals 
from  their  ores,  consisting  in  mixing  with  the  ore  a  solution  consisting  of  a  base 
and  a  solvent  for  precious  metals,  which  solvent  is  capable  of  being  separated 
from  the  said  base  by  oxygen,  and  adding  liquid  air  to  the  ore  and  solution,  or 
by  evaporating  the  nitrogen  from  liquid  air,  and  adding  the  oxygen  which  remains 
to  the  mixed  ore  and  solution. 


? — December  5,  1899.  M.  B.  ZERENER.  Precipitation  of  precious  metals 
from  their  cyanide  solutions. — The  process  of  precipitating  gold  and  silver  from 
cyanide  solutions  by  causing  the  solution  to  move  in  one  direction,  and  during 
such  movement  passing  through  it,  in  the  opposite  direction  and  in  the  form  of 
a  spray,  or  a  number  of  fine  streams  or  films,  mercury  charged  with  alkali  metal. 

641818 — January  23,  1900.  C.  WHITEHEAD.  Process  of  extracting  gold  from 
ores. — The  process  of  extracting  gold  from  ores  in  which  the  particles  of  free  gold 
are  enveloped  in  a  compound  of  a  base  metal  having  the  folio  wing  characteristics, 
to  wit:  non-siliceous,  oxidized,  practically  impervious  to  a  solvent  solution,  such 
as  one  of  cyanide,  not  readily  removable  by  washing  with  water,  and  insoluble 
in  water,  but  soluble  in  dilute  acids,  consisting  in  first  subjecting  the  crushed  ore 
to  the  action  of  heat  sufficient  to  convert  the  coating  into  a  porous  condition  and 
afterwards  treating  the  ore  with  a  cyanide  solution. 

642767 — February  6,  1900.  G.  THURNAUER.  Process  of  separating  precious 
metals  from  their  mixtures  with  zinc. — The  process  of  treating  the  mixture  of  zinc 
and  precious  metals  resulting  from  the  treatment  of  cyanide  solutions  of  the  precious 
metals  by  zinc,  which  consists  in  subjecting  said  mixture  to  the  action  of  a  solu- 
tion containing  lead  and  then  to  the  action  t>f  acid,  whereby  the  zinc  is  dissolved 
and  the  precious  metals  remain  in  admixture  with  metallic  lead. 

646006 — March  27,  1900.  J.  C.  MONTGOMERIE  and  H.  PARKES.  Treatment  of 
gold  and  silver  ores,  etc. — In  the  extraction  of  gold  and  silver  from  ores  or  compounds 
containing  the  same,  the  process  consisting  in  treating  the  ore  or  compound  with 
.a  cyanide  of  an  alkali  metal,  caustic  alkali,  and  barium  dioxide,  in  conjunction 
with  ammonium  sulphate. 

646808 — April  3,  1900.  T.  CRUSE.  Method  of  extracting  gold  and  silver  from 
iheir  ores. — The  process  of  recovering  precious  metals  from  their  ores,  which  con- 
sists in  first  heating  the  ore  pulp  to  the  boiling-point,  adding  cyanide  of  potassium 
to  the  hot  mass,  permitting  the  mass  to  gradually  cool,  and  while  it  is  cooling  add- 
ing to  the  mass  the  following:  Eluestone,  iron  sulphate,  sulphuric  acid,  and  quick- 
silver. 

649628 — May  15,  1900.  W.  A.  CALDECOTT.  Extraction  of  gold  or  other  precious 
metals  from  slimes. — The  method  of  extracting  precious  metals  from  finely  divided 
materials,  such  as  slimes,  containing  reducing  substances,  such  as  ferrous  sulphide 
or  hydrate,  which  consists  in  rendering  the  material  alkaline,  then  forcing  air 
into  the  pulp  until  the  ferrous  compounds  are  converted  into  ferric  hydrate,  then 
adding  cyanide  and  continuing  aeration  and  agitation  until  the  precious  metals 
are  dissolved. 


380  APPENDIX. 

651509 — June  12,  1900.  F.  W,  MARTINO  and  F.  STUBBS.  Precipitation  of 
precious  metals  from  cyanide  solutions. — A  process  for  the  precipitation  of  the 
precious  metals  from  their  aqueous  cyanide  solutions,  consisting  in  passing  acetylene 
and  atmospheric  air  through  such  solutions,  or  by  adding  calcium  carbide  to  them, 
and  precipitating  the  metals  in  a  metallic  state. 

651510 — June  12,  1900.  F.  W.  MARTINO  and  F.  STUBBS  Treatment  of  ores 
and  precipitation  of  precious  metals  ffom  their  cyanide  solutions. — A  process  for 
the  precipitation  of  precious  metals  from  their  aqueous-cyanide  solutions,  con- 
sisting in  treating  such  solutions  with  a  hydrocarbon  gas,  produced  when  a  metallic 
carbide  is  decomposed  by  water,  and  capable  of  precipitating  the  metals  in  a  metallic 
state.  Aluminum  carbide  is  given  as  an  example  of  such  a  metallic  carbide.  The 
use  of  methane  as  a  precipitant  is  also  claimed. 

657181 — September  4>  1900.  H.  DE  RAASLOFF.  Process  of  separating  precious 
metals  from  their  ores. — The  continuous  process  of  treating  ores  of  precious  metals, 
consisting  in  mixing  the  finely  divided  ore  with  a  suitable  solvent  for  the  precious 
metals,  inducing  the  mixture  to  flow  continuously  from  and  back  to  the  point 
of  admixture,  while  so  flowing  introducing  liquid  oxygen  or  liquefied  air  into  the 
mixture,  then  causing  the  mixture  to  flow  with  sudden  variations  of  velocity  to 
agitate  it,  then  separating  the  solution  from  the  base  earthy  mineral  matter,  and 
sending  it  continuously  through  an  electrodepositing  ,bath,  where  the  precious 
metal  is  deposited,  and  thus  in  continuous  ordered  succession. 

656395—August  21,  1900.  E.  H.  DICKIE.  Process  of  leaching  ores  or  tailings. — 
The  improvement  in  the  process  of  leaching  ores  or  tailings  with  a  solution  which 
dissolves  the  precious  metals,  which  consists  in  adding  to  the  solution  an  agent 
composed  of  an  acetate  of  an  alkali  metal  or  of  alkali-earth  metals  which  is  capable 
of  readily  uniting  with  and  forming  acetates  of  the  base  metals,  and  which  has 
little  or  no  affinity  for  the  precious  metals,  thereby  enabling  the  solvent  to  act 
directly  upon  the  latter,  and  then  leaching  the  ores.  Calcium  acetate  is  cited 
as  an  example  of  an  acetate  of  an  alkali-earth  metal. 

664080 — December  18,  1900.  J.  P.  SCHUCH,  Jr.  Process  of  extracting  precious- 
metals  from  their  ores. — A  method  of  extracting  precious  metals  from  their  ores, 
which  consists  in  combining  the  crushed  ore  with  a  cyanide  solution  while  both 
are  in  a  warm  condition,  mechanically  mixing  the  ore  and  solution  by  agitation 
simultaneously  with  the  commingling  thereof,  charging  the  mixture  during  the 
agitation  with  hot  air,  and  finally  separating  the  ore  and  slush  or  pulp  from  the 
metal  in  solution. 

665105 — January  1,  1901.  J.  C.  KESSLER.  Process  of  extracting  gold  and 
silver  from  ores. — The  process  of  separating  precious  metals  from  auriferous  and 
argentiferous  ores,  consisting,  first,  in  subjecting  the  ores  to  the  action  of  an  aque- 
ous solution,  consisting  of  cyanide  of  alkali  metal,  yellow  prussiate  of  potassium, 
and  permanganate  of  an  alkali  metal  in  substantially  the  proportions  of  water, 
one  thousand  (1000)  parts;  yellow  prussiate  of  potassium,  two  and  one-half  (2.5) 
parts;  cyanide  of  alkali,  two  and  one-half  (2.5)  parts;  parmanganate  of  potas- 
sium, one-tenth  (0.1)  part,  until  the  gold  and  silver  contained  in  such  ores  are 
dissolved;  second,  separating  the  metals  from  their  solution  by  the  application 
of  a  soluble  lead  salt,  by  which  the  cyanide  solution  is  decomposed  and  a  non- 
soluble  cyanide  of  lead  is  formed,  at  the  same  time  a  non -soluble  cyanide  of  gold 
or  silver  is  precipitated;  third,  by  the  application,  to  the  sediment  thus  precipi- 
tated, of  sodium  amalgam,  whereby  a  gold,  silver,  and  lead  amalgam  is  produced 
and  at  the  same  time  a  concentrated  solution  of  cyanide  and  ferrocyanide  of  sodium 
is  regenerated;  and,  fourth,  diluting  the  concentrated  cyanide  solution  with  a 
quantity  of  water  and  regenerating  and  reenergizing  the  aqueous  solution  for 
reuse  by  the  addition  of  permanganate  of  alkali. 

671704 — April  9,  1901.  E.  D.  KENDALL.  Process  of  treating  ores  containing1 
silver  or  silver  and  gold. — The  process  of  treating  ores  or  other  bodies  for  the  extrac- 
tion of  precious  metals,  which  consists  in  treating  them  with  a  suitable  chemical 
solution  containing  a  thiocyanate  and  a  cyanide,  capable  of  dissolving  silver  and 
gold,  and  in  then  treating  the  so-dissolved  silver  by  a  suitable  sulphide,  such  as 
potassium  sulphide,  and  in  so  regulating;  the  amount  of  the  sulphide  to  the  silver 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  381 

as  that  they  shall  substantially  equalize  each  other  in  separating  the  sulphur  sul- 
phide and  in  returning  the  thiocyanate  and  cyanide  into  subsequent  operations 
for  further  treatment  of  the  ore. 

673425 — May  7,  1901.  G.  A.  DUNCAN  and  F.  H.  BEACH.  Method  of  treating 
precious  metal-bearing  ores. — The  method  of  treatment  of  precious  metal-bearing 
ores  to  cause  the  precious  metal  to  be  dissolved  from  the  ore,  and  the  resulting 
metal-bearing  liquor  and  impoverished  ore  to  be  separated  from  each  other,  which 
consists  in  the  following  steps:  First,  maintaining  a  substantially  continuous 
supply  stream  of  mingled  comminuted  ore  and  solvent  liquor;  second,  mechani- 
cally dispersing  such  mingled  ore  and  liquor  into  the  air,  in  a  direction  transverse 
to  the  onward  movement  of  the  stream,  without  separating  the  ore  from  the  liquor; 
third,  delivering  the  resultant  stream  of  mingled  metal-bearing  liquor  and  impov- 
erished ore  and  receiving  the  same  in  mingled  condition  and  carrying  it  onward; 
fourth,  sucking  the  liquor  from  the  tailings;  fifth,  delivering  water  to  the  impov- 
erished tailings  remaining,  and  subsequently  sucking  such  wash-water  therefrom;, 
sixth,  delivering  such  impoverished  ore  or  tailings  after  the  application  cf  such 
suction. 

682612 — September  17,  1901.  E.  L.  GODBE.  Method  of  leaching  ores. — The- 
method  of  leaching  ores,  which  consists  in  disposing  moistened  ore  in  superim- 
posed strata  within  a  containing  receptacle  by  a  continuous  mechanical  agitation 
in  the  lower  portion  of  the  latter  to  form  a  lower  thoroughly  agitated  stratum  of 
heavier  portions  of  the  ore,  a  stratum  of  lighter  portions  or  particles  next  above 
which  are  agitated  to  a  less  degree,  a  stratum  of  slimes  and  other  lighter  particles 
next  above  which  remain  substantially  immobile,  and  a  top  covering  of  a  clear 
supernatant  solution,  introducing  the  ore  below  the  upper  surface  of  said  latter 
solution,  overflowing  and  carrying  off  the  clear  solution,  replacing  water  in  the 
charge  by  a  cyanide  of  potassium  solution  introduced  at  the  bottom  of  the  recep- 
tacle below  the  lower  heavier  stratum  and  causing  it  to  percolate  upwardly  through 
the  strata  above,  increasing  the  agitation  during  the  introduction  of  said  cyanide 
solution,  carrying  off  the  metal-bearing  cyanide  solution  which  overflows  from  the 
top  of  the  charge  and  precipitating  the  said  overflow  metal-bearing  solution  after 
it  leaves  the  receptacle. 

689190—December  17,  1901.  B.  HUNT.  Process  of  precipitating  and  recover- 
ing precious  metals  from  their  solutions. — -The  process  of  precipitating  precious 
metajs,  consisting  of  adding  to  the  pulp  a  cyanide  solution  and  agitating  the  same 
until  the  metal  is  extracted;  then  adding  to  the  pulp,  while  continuing  the  agita- 
tion thereof,  powdered  metallic  aluminum  whereby  the  precious  metal  is  precipi- 
tated, but  in  suspension  in  the  pulp;  then  adding  mercury  and  continuing  the 
agitation  until  the  metal  is  in  the  form  of  an  amalgam,  and  finally  recovering 
the  precious  metal  by  treating  the  amalgam. 

692634- — February  4>  1902.  H.  DAVIS.  Process  of  extracting  precious  metals 
from  their  ores. — A  process  for  the  extraction  of  the  precious  and  other  metals 
from  ore,  ore  pulp,  sands,  slimes,  tailings,  mineral-bearing  earths  or  other  sub- 
stances containing  these  metals,  which  consists  in  introducing  chlorine  gas  into 
the  ore  and  afterwards  wholly  or  partially  removing  the  excess  of  chlorine  by 
forcing  air  into  the  material  and  afterwards  treating  with  a  cyanide  solution  to- 
dissolve  the  chlorides. 


f — March  4,  1902.  B.  W.  BEGEER.  Cyanide  process  of  extracting  pre- 
cious metals  from  ores. — The  process  of  treating  material  containing  the  precious 
metals,  consisting  in  setting  in  motion  in  an  endless  path  a  solution  of  cyanide 
of  potassium,  introducing  oxygen  to  the  moving  liquid,  and  finally  subjecting 
the  metal-bearing  material  to  the  action  of  said  solution. 


£ — March  25,  1902.     E.  SCHILZ.     Cyanide  process  of  extracting  precious 
metals  from  their  ores. — An  improved  process  in  the  art  of  extracting  precious    v  v 
metals  from  their  ores,  said  process  consisting  in  thoroughly  and  intimately  mix- 
ing peroxide  of  barium   (BaO2)  with  precious  metal-bearing  rraterial,  and  then 
subjecting  the  same  to  treatment  with  an  alkaline-cyanide  solution. 

701002— May  27,  1902.     J.  B.  DE  ALZUGARAY.     Method  of  extracting  precious 
metals  from  their  ores. — The  process    for  treating  ores  containing  precious  metal 


,382  APPENDIX. 

and  consisting  in  adding  the  crushed  ore  to  a  solution  of  sodium  chloride,  sodium 
carbonate,  and  potassium  cyanide,  then  forcing  through  the  mass  a  gaseous  mix- 
ture of  bromine  and  air  and  recovering  the  precious  metals  from  the  solution  by 
any  known  means,  such  as  electrolysis. 

702305 — June  10,  1902.  E.  D.  KENDALL.  Process  of  extracting  precious 
metals  from  their  ores. — The  process  of  treating  ores  carrying  precious  metals, 
which  consists  in  treating  such  ore  with  a  lixiviating  solution,  consisting  of  a  cyanide, 
potassium  percarbonate,  and  water,  and  finally  extracting  the  precious  metal  from 
such  lixivium. 

705698— July  29,  1902.  R.  H.  OFFICER,  J.  W.  NEIL,  J.  H.  BURFEIND,  and 
F.  H.  OFFICER.  Cyanide . process  of  working  gold,  silver,  or  other  ores. — The  im- 
provement in  treating  ores  by  the  cyanide  process,  consisting  in  agitating  the 
pulp  containing  the  cyanide  solution  by  a  suitable  gas  under  pressure,  passing 
the  gas  and  the  hydrocyanic-acid  gas  liberated  from  the  solution  through  a  regen- 
erating solution,  and  using  the  gas  after  passing  through  said  regenerating  solu- 
tion to  agitate  a  fresh  quantity  of  pulp. 

708303 — August  5,  1902.  L.  B.  DARLING.  Process  of  extracting  precious 
metals  from  ores. — The  process  of  extracting  precious  metals  from  finely  divided 
materials  or  ores,  which  consists  in  spreading  a  comparatively  thin  layer  of  the 
material  over  a  substantially  flat  and  large  working  surface  provided  with  drain- 
age ducts  or  channels;  then  covering  said  material  with  suitable  metal-dissolving 
or  cyanide  solution;  then  passing  a  heavy  roll  back  and  forth  over  the  charge 
of  material,  etc.,  thereby  at  the  same  time  thoroughly  agitating  or  stirring  the 
charge  and  forcing  some  of  the  solution  into  the  drainage  ducts;  then  discharg- 
ing said  solution  into  the  sump,  and  finally  precipitating  the  precious  metal  from 
the  solution. 

707926 — August  26,  1902.  W.  HILT  and  C.  E.  LANE.  Process  of  extracting 
precious  metals. — The1  process  of  extracting  precious  metals  from  solutions  thereof, 
which  consists  in  producing  cyanide  solutions  of  said  metals,  vaporizing  metallic 
^inc  by  means  of  heat,  and  conducting  the  vapor  thus  formed  to  a  point  beneath 
the  surfaces  of  said  solutions,  thus  producing  finely  divided  zinc,  which  replaces 
the  precious  metals  and  thereby  causes  their  precipitation. 

708504 — September  2,  1902.  H.  L.  SULMAN  and  H.  F.  KIRKPATRICK-PICARD. 
Treatment  of  ore  slimes. — The  process  of  treating  ore  slimes,  which  consists  in  sepa- 
rating, by  means  of  a  centrifugal  machine,  the  ore  slimes  from  the  residual  water 
with  which  they  are  mixed  by  adding  a  little  lime  to  the  charge,  removing  the 
bulk  of  the  water,  thereafter  introducing  into  the  machine  an  amount  of 
leaching  solution  of  a  volume  equal  to  that  of  the  remaining  quantity  of  adhering 
moisture  and  introduced  into  the  slimes  by  centrifugal  action,  and  replacing  ]the 
moisture  by  the  added  leaching  solution. 

710496 — October  7,  1902.  S.  T.  MUFFLY.  Process  of  treating  ores. — The  process 
of  treating  ores,  which  consists  in  injecting  into  said  ores,  as  they  are  agitated 
and  elevated  and  allowed  to  fall  by  gravity  in  a  closed  chamber,  a  chemical  solu- 
tion in  the  form  of  a  spray,  together  with  hot  air  under  pressure,  and  allowing 
the  elements  and  fumes  freed  by  this  operation  to  escape  from  said  chamber. 

718633 — January  20,  1903.  T.  B.  JOSEPH.  Gold-extracting  process. — The 
process  of  extracting  gold  or  silver  from  ore  containing  the  same,  when  in  a  suit- 
able condition,  which  consists  in  subjecting  the  said  ore  to  the  leaching  action  of 
a  solution  of  water,  cyanide  of  potassium,  hydrate  of  calcium,  and  carbonic-acid 
gas,  and  introducing  an  oxidizing  agent  into  the  solution,  and  subsequently  pre- 
cipitating the  gold  from  this  solution. 

719274 — January  27,  1903.  Z.  B.  STUART.  Process  of  extracting  metals  from 
ores. — The  process  of  extracting  precious  metals  from  ores,  consisting  in  agitating 
the  pulp  together  with  cyanide,  water,  and  air  by  ebullition  in  one  vessel, 
causing  the  mixture  to  assume  an  even  consistency  throughout,  and  passing  the 
mixture  through  a  mechanical  agitator  and  combining  therein  a  relatively  smaller 
•quantity  of  mixture  with  a  relatively  larger  quantity  of  air  and  there  forcing  the 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  383 

pulp,  cyanide,  water,  and  air  into  intimate  contact,  and  circulating  the  mixture 
through  the  two  vessels. 

722455 — March  10,  1903.  AUGUST  PRISTER  Process  of  precipitating  gold 
from  cyanide  solutions. — The  process  for  the  precipitation  of  gold  or  other  precious 
metals  from  cyanide  solutions,  such  as  potassium  cyanide,  sodium  cyanide,  and  V/ 
bromine  cyanide,  which  consists  in  acidifying  the  solution,  adding  a  solution  con- 
taining  salts  of  mercury  and  copper,  and  then  adding  a  solution  containing  zinc 
salts  and  a  small  percentage  of  a  potassium  ferrocyanide,  or  a  small  quantity  of 
the  cyanide  solution  discharged  from  the  ordinary  zinc-precipitation  Boxes. 


? — March  17,  1903.  J.  P.  SCHUCH,  Jr.  Process  of  separating  precious 
metals  from  solvent  solutions. — The  process  of  separating  precious  metals  from 
their  solvent  solutions,  which  consists,  first,  in  passing  the  solution  through 
crushed  limestone  or  phonolite  to  neutralize  any  free  acid,  then  through  zinc, 
wood  ashes,  asbestos  wool  or  its  equivalent,  and  charcoal  or  coke,  to  neutralize 
any  free  soda  or  carbonates,  then  through  zinc  shavings  to  precipitate  the  pre- 
cious metals,  then  through  charcoal  to  filter  the  solution  and  effect  retention  of 
a  percentage  of  the  precious  metals,  then  through  limestone  or  crushed  phono- 
lite  to  effect  precipitation  of  zinc  contained  in  the  solution,  and  then  alternately 
through  zinc,  charcoal,  or  coke  and  zinc  to  effect  complete  separation  of  the  pre- 
cious metals  and  thorough  filtration  of  the  solution. 

725895 — April  21,  1903.     M.  V.  USLAR  and  G.  ERLWEIN.     Process  of  extract- 
ing gold. — The  process  for  extracting  gold  from  auriferous  ores,  which  consists  in     x\ 
lixiviating  the  ores  with  a  solution  of  potassium  cyanide,  rhodanides,  hyposul- 
phites, and  sodium  chloride. 

726294 — April  28,  1903,  F.  J.  HOYT.  Method  of  extracting  gold  from  ores. — 
The  method  of  milling  gold  ore,  consisting  of  the  following  steps:  First,  pulverizing 
the  ore;  second,  distributing  the  ore  thinly  over  a  wide,  long,  and  open  sluice- 
way; third,  flowing  the  ore  and  propelling  it  forward  over  its  bed  by  the  action  of 
a  stream  of  chemical  solution  adapted  to  dissolve  the  ore;  fourth,  automatically 
screening  and  separating  the  solution  from  the  tailings  by  the  same  force;  and 
fifth,  subjecting  the  solution  to  a  reagent  to  precipitate  the  gold  therein. 

727659— May  12,  1903.     F.  W.  MARTINO.     Method  of  extracting  noble  metals. 
— The  process  of  recovering  gold  from   its  cyanide  solution,  consisting  in  acidify-     ,, 
ing  the  solution  and  treating  it  at  a  raised  temperature  with   barium  sulphocar-  "; 
bide.     The  latter  is  manufactured  by  fusing  two  parts,  by  weight,  of  barium  sul- 
phate (baryta  or  heavy  spar)  BaSO4  in  an  electric  furnace  with  one  part  of  carbon. 

728397— May  19,  1903.  T:  B.  JOSEPH.  Gold-extracting  process. — The  process 
of  extracting  gold  and  silver  from  ore  containing  the  same  when  in  a  suitable  con- 
dition, which  consists  in  subjecting  the  said  ore  to  the  leaching  action  of  a  solu- 
tion of  water,  cyanide  of  potassium,  hydrate  of  calcium,  peroxide  of  barium  and 
carbonic-acid  gas,  the  ore  being  agitated  by  compressed  air. 

730835 — June  9,   1903.     D.    MOSHER.     Ammonia  cyanide   process   of  treating 
copper,  nickel,  or  zinc  ores  containing  precious  metals. — The  process  of  treating 
refractory  sulphur,  tellurium,  and  arsenical  ores  containing  copper,  zinc,  nickel, 
gold,  and  silver,  consisting  in  first  roasting  such  ores  at  a  low  red  heat  to  trans- 
form the  metals  so  transformable  into  sulphates,  arsenates,  or  tellurates;    then    -N/V1 
oxidizing  reducing  compounds  by  very  dilute  ammonia;  and  subsequently  extract-    ' 
ing  the  metals  with  an  ammoniacal-cyanide  solution  containing  an  excess  of  cupric 
oxide  or  hydroxide  over  and  above  that  necessary  to  form  metallic  cyanide  double 
salts. 

731169 — June  16,  1903.  O.  A.  ELLIS.  Apparatus  for  extracting  metals  from 
ores. — An  apparatus  for  extracting  metals  from  ores,  having  in  combination 
a  receiving  hopper  having  an  inclined  bottom,  a  discharge  opening  in  said  hopper, 
an  inclined  chute  leading  from  said  hopper  and  provided  with  a  screen,  a  pre- 
cipitating box  connected  with  said  inclined  chute,  means  for  causing  a  flow  of 
chemical  solution  through  said  hopper,  chute,  and  precipitating  box,  and  means 
for  passing  a  current  of  electricity  through  said  precipitating  box. 


384  APPENDIX. 

731631 — June  23,  1903.  J.  T.  TERRY,  Jr.  Extracting  gold  or  silver  from, 
slimes. — An  improvement  in  separating  precious  metals  from  slimes  with  which 
they  are  mixed,  consisting  in  forming  a  solution  with  water,  spraying  said  solu- 
tion into  tanks  containing  a  cyanide  solution  made  dense  by  the  addition  of  salt, 
allowing  the  slime  to  settle  through  and  into  the  solution,  then  drawing  the  clear 
liquor  from  the  top  through  vertically  disposed  filters  and  discharging  the  sludge 
from  the  bottom  into  succeeding  tanks  containing  a  similar  cyanide  solution, 
allowing  it  to  settle  and  again  drawing  off  the  clear  liquor. 

731839 — -June  23,  1903.  G.  A.  BAHN.  Sulphuric  acid  process  of  extracting- 
precious  metals  from  solutions. — The  process  of .  precipitating  precious  m3tals  from 
solutions  thereof,  which  consists  in  producing  cyanide  solutions  of  said  precious 
metals,  then  acidulating  with  sulphuric  acid  said  cyanide  solutions,  then  immers- 
ing zinc  in  sheet,  plate,  or  other  form  in  the  acidulated-cyanide  solution  contain- 
ing the  precious  metals;  the  chemical  action  thereupon  taking  place  in  the  solu- 
tion, dissolving  zinc  and  precipitating  the  precious  metals;  then  recovering  from 
the  precipitate  of  the  preceding  operation  the  precious  metals  by  filtering  and 
melting,  or  other  process. 

732605 — June  30,  1903.  G.  E.  THEDE.  Process  of  leaching  ores. — The  proc- 
ess of  leaching  ores  which  consists  in  mixing  with  the  ore  to  be  treated  a  cyanide 
solution,  peroxide  of  hydrogen,  and  an  oxide  which  is  reducible  by  said  peroxide  of 
hydrogen. 

732639 — June  SO,  1903.  T.  B.  JOSEPH.  Gold-extracting  process. — The  process 
of  extracting  gold  and  silver  from  ore  containing  the  same,  when  in  a  suitable 
condition,  which  consists  in  subjecting  said  ore  to  the  leaching  action  of  a  solution 
containing  water,  cyanide  of  potassium,  bromine,  hydrate  of  calcium,  peroxide 
of  barium,  and  carbon  dioxide,  said  carbon  dioxide  being  forced  into  the  leaching 
solution  simultaneously  with  compressed  air. 

738758 — September  15,  1903.  J.  B.  DE  ALZUGARAY.  Extraction  of  precious 
metals  from  their  ores. — The  process  for  extracting  precious  metals  from  their 
ores,  consisting  in  first  moistening  the  crushed  ore  with  an  alkaline  solution  and 
afterwards  agitating  it  in  a  solvent  solution  and  blowing  through  it  an  oxidizing 
agent  composed  of  gaseous  bromine,  and  its  acid  and  oxyacid  compounds  dissolved 
in  air,  and  finally  recovering  the  metals  from  the  solvent  in  any  well-known  manner 

745490— December  1,  1903. — T.  J.  GRIER.  Process  of  extracting  precious  metals. 
— The  process  of  extracting  precious  metals  from  slimes,  consisting  in  directing  the 
slimes  into  a  settling-tank,  drawing  off  the  thicker  portions  of  the  slimes  and 
depositing  the  same  into  a  leaching-vat,  of  introducing  a  cyanide  solution  under 
pressure  through  perforations  in*  the  false  bottom  of  the  vat,  causing  the  watery 
portions  of  the  slimes  to  be  displaced  by  said  cyanide  solution,  then  treating  the 
charge  with  an  air  under  pressure,  and  afterwards  introducing  through  the  false 
bottom  of  a  vat  a  salt  solution  of  greater  density  than  the  cyanide  solution  to 
displace  the  latter. 

745828 — December  1,  1903.  E.  B.  HACK.  Process  of  extracting  metals  from 
ores. — A  cyanide  process,  consisting  of  the  following  steps  in  the  order  named: 
Caking  the  pulp  by  pressure  under  conditions  allowing  the  moisture  to  escape; 
introducing  a  weak  solution  of  the  solvent  simultaneously  with  the  introduction 
of  air  under  pressure;  drying  the  pulp  by  passing  air  under  pressure  therethrough; 
introducing  a  stronger  solution  of  the  solvent  simultaneously  with  the  introduc- 
tion of  air  under  pressure;  and  finally  drying  the  cake  by  air  pressure. 

755951 — March  29,  1904-  J.  SMITH.  Process  of  treating  ores. — In  the  cyanide 
treatment  of  ores,  the  method  of  rendering  insoluble  in  the  cyanide  solution  ferrous 
oxide  contained  in  a  mass  of  moist  crushed  ore,  which  method  consists  in  apply- 
ing heat  to  said  mass  in  the  presence  of  air,  previous  to  >its  treatment  by  the 
cyanide  solution. 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  385 

CLASS  204— ELECTROLYSIS. 

Subclass  15 — Aqueous  Bath,    Ores. 

61866 — February  5,  1867.  J.  H.  RAE.  Improved  mode  of  treating  auriferous 
and  argentiferous  ores. — This  invention  consists  in  treating  auriferous  and  argen- 
tiferous ores  with  a  current  of  electricity  or  galvanism  for  the  purpose  of  separat- 
ing the  precious  metals  from  the  gangue.  In  connection  with  the  electric  current 
suitable  liquids  or  chemical  preparations,  such,  for  instance,  as  cyanide  of  potas- 
sium, are  used,  in  such  a  manner  that  by  the  combined  action  of  the  electricity 
and  of  the  chemicals,  the  metal  contained  in  the  ore  is  first  reduced  to  a  state  of 
solution  and  afterwards  collected  and  deposited  in  a  pure  state.  Among  the 
claims  is  one  for  the  use  of  the  platinum  agitator  as  an  electrode. 

Q2776 — March  12,  1867.  J.  H.  RAE.  Improved  mode  of  collecting  gold  and 
silver  from  sweepings,  washings,  etc. — This  invention  consists  in  treating  sweepings, 
filings,  and  washings  containing  gold  or  silver  with  a  current  of  electricity  or  gal- 
vanism for  the  purpose  of  separating  the  precious  metals  from  the  impurities  of 
foreign  matter  mixed  with  them.  In  connection  with  the  electric  current  suitable 
liquids  or  chemical  preparations,  such,  for  instance,  as  cyanide  of  potassium, 
are  used  in  such  a  manner  that  by  the  combined  action  of  the  electricity  and  chemi- 
cals the  precious  metals  contained  in  the  sweepings,  filings,  and  washings  are 
first  reduced  to  a  state  of  solution,  and  afterwards  collected  and  deposited  either 
as  oxides  or  in  a  metallic  state,  and  the  operation  of  extracting  or  separating  said 
precious  metals  from  the  sweepings,  filings,  or  washings  is  attended  with  very 
little  trouble  and  expense.  During  this  operation  the  bath  which  contains  the 
washings,  filings,  or  sweepings  acts  as  an  electrode,  and  also  as  an  agitator;  and 
the  third  claim  of  the  patent  covers  the  use  of  this  carbon  electrode  as  an  agitator. 

90565 — May  25,  1869.  W.  J.  LYND.  Improved  process  of  separating  iron 
and  other  metals  from  potters'  clay. — The  process  of  removing  iron,  copper,  and 
other  discoloring  matters  from  potters'  clay  and  other  argillaceous  substances  by 
subjecting  the  clay,  when  in  solution,  to  the  action  of  one  or  more  magnets,  or 
by  passing  through  the  bath  containing  such  solution  a  current  of  electricity. 

239300 — March  22,  1881.  A.  RYDER.  Apparatus  for  treating  ores. — The 
invention  has  reference  to  apparatus  for  reducing  ores  in  which  the  ore,  while  in 
a  heated  state,  is  dumped  suddenly  into  a  liquid  or  chemical  solution  for  the  pur- 
pose of  disintegrating  the  ore  and  separating  the  particles  preparatory  to  amal- 
gamation. And  the  inventor  claims,  in  an  apparatus  for  disintegrating  ores  pre- 
paratory to  amalgamation,  the  insulated  vessel  or  non-conductor  of  electricity, 
provided  with  a  metallic  or  plated  hopper,  in  combination  with  an  electrical  gen- 
erator or  battery  and  conducting  wire  or  wires. 

246201 — August  23,  1881.  E.  REYNIER.  Electrochemical  treatment  of  ores. — 
The  method  of  treating  ores  of  zinc  and  lead  for  the  production  of  electricity  and 
recovery  of  the  metals  by  acting  upon  said  ores  in  a  voltaic  couple  with  an  elec- 
trolytic liquid  haying  caustic  alkali  as  the  base,  and  precipitating  the  metallic 
oxides  from  said  liquid. 

272391 — February    13,    1883.     A.    THIOLLIER.     Process    of    and  apparatus  for 
extracting  metals  from  their  ores. — In  combination  with  an  electrogenerator,  a  recep- 
tacle for  conductively  prepared  ore  or  other  material  containing  metal  to  be  recov-        / 
ered,  having  attachments  for  the  negative  and  positive  polar  conductors   of  thex^ 
electrogenerator,   arranged,   as   described,   in   electrical   communication   with   the    / 
mass  of  conductive  ore  by  means  of   the  electrolytic  solution,  whereby  reduction 
is  effected  when  the  current  is  passed. 

286208 — October  9,  1883.  L.  LETRANGE.  Process  of  and  apparatus  for  reducing 
zinc  ores. — The  process  of  reducing  zinc  ores  and  producing  pure  metallic  zinc 
and  sulphuric  acid  simultaneously  therefrom,  which  consists  in  simultaneously 
roasting  sulphuret  ores  and  carbonate  ores  in  the  fame  or  communicating  chambers, 
and  thereby  converting  both  ores  into  soluble  sulnhates,  then  leaching  these  roasted 
ores,  and  then  depositing  the  metallic  zinc  from  a  solution  of  the  sulphates  by 


386  APPENDIX. 

electric  currents  on  metallic  plates,  and  drawing  sulphuric  acid  at  the  same  time 
from  the  solution  as  fast  as  set  free  by  the  said  electric  currents;  and  the  appa- 
ratus for  use  in  the  process  of  reducing  zinc  ores,  which  consists,  essentially,  in  a 
reservoir  for  the  sulphate  solution;  a  precipitating  vessel  provided  with  suitable 
anodes  and  cathodes;  a  pipe  provided  with  a  regulating  cock,  leading  from  the 
reservoir  to  near  the  bottom  of  the  precipitating  vessel,  and  an  outlet  pipe  for 
the  freed  acid,  arranged  in  the  said  vessel  at  the  desired  level  of  the  liquid  therein, 
whereby  the  strength  and  quantity  of  the  sulphate  solution  in  the  precipitating 
vessel  are  maintained  constant. 

291670 — January  8,  1884.  M.  BODY.  Process  of  and  apparatus  for  obtain- 
ing gold  and  silver  from  their  ores  by  combined  electrolytic  and  amalgamating  proc- 
esses.— The  method  of  first  subjecting  gold  and  silver  ores  to  the  action  of  ferric 
salts,  in  combination  with  the  electrolytic  process,  and  the  subsequent  amalga- 
mation of  the  metals  with  mercury  under  the  continued  action  of  the  electric  cur- 
rent: and  the  apparatus  for  effecting  this  process. 

300950— June  24,  188 '4.  H.  R.  CASSEL.  Process  of  and  apparatus  for  the 
separation  of  metals  from  ores  and  alloys. — The  process  of  separating  metals  from 
ores  or  alloys,  especially  those  of  an  auriferous  character,  which  consists  in  charg- 
ing the  ore  or  alloy  in  a  powdered  condition  into  an  anode  compartment,  which 
is  separated  from  the  cathode  compartment  by  porous  material,  said  anode  com- 
partment containing  a  solution  yielding  nascent  chlorine  under  the  action  of  an 
electric  current,  and  agitating  said  powdered  material  within  said  solution  during 
the  passage  of  the  electric  current;  and  the  combination  in  an  apparatus  for  treat- 
ing ores  and  metals  by  electrolysis,  of  a  cathode  compartment,  a  negative  pole 
therein,  a  rotary  drum  constituting  the  anode  compartment,  provided  with  por- 
ous material  separating  it  from  the  cathode  compartment,  and  with  a  series  of 
carbon  rods  or  plates  arranged  within  the  same,  and  suitable  electric  connections. 

800951 — June  24,  1884.  H.  R.  CASSEL.  Process  of  chloridizing  ores  by  elec- 
trolysis— In  the  process  of  extracting  gold  from  rebellious  or  refractory  gold  ores, 
the  steps  which  consist  in  subjecting  the  ore  to  the  action  of  a  solution  yielding 
nascent  chlorine  under  electrolytic  decomposition,  and  adding  lime  or  its  equiv- 
alent, whereby  acids  formed  by  secondary  action  during  said  decomposition  are 
neutralized. 

317245 — May  5,  1885.  E.  P.  THOMPSON.  Apparatus  for  the  separation  of 
gold  from  its  ores  by  electrochlorination  and  deposition. — The  combination,  with 
an  electrolytic  cell  for  separating  chlorine  from  its  compounds  and  its  anode,  of 
a  battery,  a  cathode  consisting  of  a  pipe  through  which  steam  is  admitted  to 
the  cell  for  the  purpose  of  increasing  the  rapidity  of  the  separating,  and  conduc- 
tors respectively  connecting  the  same  anode  and  cathode  with  the  poles  of  said 
battery. 

317246 — May  5,  1885.  E.  P.  THOMPSON.  Apparatus  for  the  electrodeposition 
of  gold  from  its  chlorides. — The  combination,  in  an  electrolytic  cell,  of  an  anode 
formed  of  a  series  of  carbon  rods  set  in  a  metal  ring,  and  a  cathode  formed  by  two 
thin  corrugated  copper  plates  connected  electrically,  which  are  set,  respectively, 
within  and  without  the  circle  of  carbons. 

332705 — December  22,  1885,  H.  H.  EAMES.  Apparatus  for  chloridizing  goldt 
silver,  and  other  ores. — This  invention  consists  of  an  iron  vessel  cylindrical  in  shape, 
lined  with  wood,  having  a  cast-iron  cover,  adjusted  so  as  to  be  steam-  and  vapor- 
tight.  It  is  also  arranged  with  a  set  of  stirrers,  to  which  motion  is  communicated 
by  crown-  and  pinion- wheels.  It  is  also  fitted  with  pipes,  by  means  of  which  steam 
can  be  forced  through  the  contents  and  held  there  under  pressure.  It  is  also 
furnished  with  two  electrodes,  by  which  electricity  can  be  passed  through  the 
ore  and  chemicals  operated  upon,  while  the  pressure  is  applied.  The  electric 
current  is  best  obtained  from  a  dynamo  machine  of  ordinary  construction  used 
in  the  deposition  of  metals. 

333815 — January  5,  1886.  M.  BODY.  Process  of  obtaining  gold,  silver,  copper, 
nickel,  and  cobalt  from  their  ores  by  electrolytic  action. — The  process  of  separating 
gold,  silver,  copper,  and  other  metals  from  chlorinated  or  chlorine-containing 
ores  by  electrolytic  action,  consisting  in  first  roasting  the  ores  or  subjecting  them 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  387" 

to  an  equivalent  oxidizing  treatment,  as  specified,  and  then  subjecting  the  ore 
to  the  action  of  ferric-salt  solutions,  and  at  the  same  time  passing  an  electric  cur- 
rent through  said  solution,  whereby  the  metal  becomes  dissolved  and  precipitated, 
and  chlorine  gas  is  generated  at  the  positive  pole,  which  reconverts  the  resulting 
ferrous  salts  into  ferric  salts. 

351576 — October  26,  1886.  H.  R.  CASSEL.  Process  of  extracting  gold,  etc.,, 
from  ores. — The  process  of  separating  metals  from  ores  or  alloys,  especially  those 
of  an  auriferous  character,  which  consists  in  charging  the  ore  or  alloy  in  a  pow- 
dered condition,  into  an  anode  compartment,  which  is  separated  from  the  cathode 
compartment  by  a  porous  partition  composed  of  asbestos,  which  permits  the  pas- 
sage of  the  current  with  the  metals  in  solution,  and  retains  the  ores  within  the 
anode  compartment,  said  anode  compartment  containing  a  chloride  solution, 
agitating  and  subjecting  the  charge  to  nascent  chlorine  produced  from  said 
solution  during  the  passage  of  the  electric  current,  passing  the  solution  of  metals 
through  the  asbestos  partition,  and  depositing  the  metals  in  solution  at  the 
cathode. 

357659 — February  15,  1887.  D.  G.  FITZGERALD.  Obtaining  chlorine  by  electroly- 
sis.— The  electrochemical  generation  of  chlorine  by  means  of  an  anode  of  per- 
oxide of  lead  in  the  form  of  dense,  highly  conductive  layers,  plates,  or  masses  of 
any  required  form  preferably  obtained  by  the  means  hereinbefore  described,  the 
said  anode  being  employed  in  conjunction  with  any  suitable  cathode  and  with 
an  electrolyte  capable  of  evolving  chlorine. 

360852 — April  12,  1887.  H.  R.  CASSEL.  Apparatus  for  separating  metals 
from  ores  or  alloys. — In  an  apparatus  for  separating  metals  from  ores  or  alloys 
by  electrolysis  the  combination  of  a  journaled  drum  provided  with  carbon  anodes, 
a  hollow  metallic  shaft  insulated  on  its  exterior  and  extending  through  said  drum, 
said  shaft  being  perforated  within  the  drum  and  separated  from  the  interior  there- 
of by  a  filter,  and  a  screw  conveyor  within  said  hollow  shaft. 

360853 — April  12,  1887.  H.  R.  CASSEL.  Apparatus  for  separating  meals 
from  ores  or  alloys. — In  an  apparatus  for  separating  metals  from  ores  or  alloys  by 
electrolysis  the  combination  of  a  rotary  drum  constituting  the  anode  compart- 
ment and  having  a  suitable  electric  connection,  a  rotary  cathode  compartment 
having  a  suitable  electric  connection  and  provided  with  an  automatic  valve,  a 
porous  diaphragm  separating  said  anode  and  cathode  compartments,  a  fixed 
bracket,  and  an  arch-shaped  arm  attached  to  said  bracket  in  the  path  of  said  valve 
for  opening  of  the  latter. 

362022 — April  26,  1887.  H.  LIEPMANN.  Apparatus  for  separating  metals  from 
ores  or  alloys  by  electrolysis. — In  an  apparatus  for  separating  metals  from  ores 
or  alloys  by  electrolysis  the  combination  of  an  anode  compartment,  a  cathode 
compartment,  a  filtering  diaphragm  separating  said  compartments,  a  dense  por- 
ous diaphragm  for  separating  said  compartments  during  one  step  of  the  operation, 
and  mechanism  whereby  the  dense  porous  diaphragm  may  be  placed  in  opposition 
with  or  removed  from  the  opening  between  the  anode  and  cathode  compartments. 

379764 — March  20,  1888.  C.  F.  CROSELMIRE.  Wet  process  of  extracting  pure 
zinc  from  its  ores. — The  process  which  consists  in  immersing  roasted  zinc  ore  in 
dilute  acid,  passing  an  air  blast  through  the  solution  until  the  impurities  are  oxi- 
dized, and  finally  drawing  off  the  zinc  solution  and  depositing  or  precipitating  the 
zinc. 

387036 — July  31,  1888.  C.  P.  BELLOWS.  Process  of  cleansing  gold  and  silver 
where  mechanically  coated  in  ores  with  refractory  substances. — The  process  of  cleans- 
ing refractory  ores  prior  to  the  recovery  of  the  precious  metals  therefrom,  which 
consists  in  immersing  said  ores  in  a  solution  of  a  sodium  chloride  and  caustic 
soda,  heating  said  solution,  and  at  the  same  time  subjecting  the  ores  to  the  action 
of  the  electric  current,  whereby  the  ore  is  rendered  free  milling. 

391360— October  16,  1888.  H.  H.  EAMES.  Apparatus  for  chloridizinq  ores.— 
In  a  device  for  chloridizing  metallic  ores,  the  combination  of  a  hermetically  sealed 
tank,  metallic  plates  placed  inside  the  said  tank  and  mounted  upon  insulated  sup- 
ports, whereby  they  will  be  insulated  from  each  other  and  from  the  tank,  the  said 
plates  forming  the  two  elements  of  a  galvanic  battery,  a  stirrer  placed  in  the  said 


388  APPENDIX. 

tank  and  between  the  said  plates  a  solution  containing  the  ore  to  be  treated,  by 
which  a  galvanic  current  will  be  excited  between  the  said  charging  steam  in  the 
said  tank,  whereby  the  said  solution  will  be  heated  and  a  pressure  maintained  in 
said  tank. 

399209 — March  5,  1889.  J.  H.  RAE.  Electric  amalgamator. — In  an  apparatus 
for  working  ores,  a  pan  or  tub  with  an  internal  copper  ring  and  rotating  arms  or 
stirrers,  in  combination  with  a  horizontal  wooden  ring  suspended  above  the  tub, 
a  copper  plate  forming  the  upper  surface  of  said  ring  and  perforated  to  admit  car- 
bons which  pass  loosely  through  the  plates,  said  carbons  having  heads  or  trans- 
verse pins  at  the  upper  ends,  and  the  movable  elastic  plates  or  springs  pressing 
upon  the  heads  of  the  carbons  to  hold  them  in  contact  with  the  copper  plate. 

407386 — July  23,  1889.  J  C.  WISWELL.  Bath  or  solution  for  separating  metals 
from  their  ores. — The  process  of  producing  a  bath  or  solution  for  the  separation  of 
metals  from  their  ores,  consisting  in  subjecting  a  solution  of  salt  water,  muriate  of 
ammonia,  and  muriatic  acid  to  a  current  of  electricity,  then  placing  this  solution 
in  a  tank  containing  liquid  mercury,  and  subjecting  the  whole  to  a  current  of  elec- 
tricity, said  mercury  serving  as  the  anode. 

410228 — September  3,  1889.  J.  C.  WISWELL.  Solution  for  use  in  separating 
metals  from  their  ores. — A  solution  or  bath  for  use  in  separating  metals  from  their 
ores,  consisting  of  chlorine  in  solution,  sodium  chloride,  ammonium  chloride, 
hydrochloric  acid,  and  bichloride  of  mercury. 

415576 — November  19,  1889.  W.  VON  SIEMENS.  Process  of  electrodeposition 
of  metals. — The  process  which  consists  in  lixiviating  ore  in  separate  vessels  with  a 
solution  containing  ferric  sulphate,  passing  the  resulting  ferrous  sulphate  succes- 
sively through  a  series  of  compartments  containing  cathode  plates,  and  in  which 
cells  the  solution  is  subjected  to  the  action  of  an  electrical  current  by  which  the 
metal  in  solution  is  deposited,  then  passing  the  remaining  liquid  successively 
through  a  second  series  of  compartments  containing  anode  plates  of  insoluble 
material  and  separated  from  the  first-mentioned  compartments  by  non-metallic 
diaphragms,  whereby  the  ferrous  sulphate  is  oxidized  and  reconverted  into  ferric 
sulphate,  which  solution  is  again  used  to  lixiviate  ores. 

418134 — December  24,  1889.  H.  F.  JULIAN.  Process  of  extracting  gold  and 
silver  from  their  ores. — The  improvement  •  in  the  process  of  extracting  gold  and 
silver  from  ores,  which  consists  in  agitating  the  pulverized  ore  in  closed  vats  with 
chlorine,  bromine,  or  iodine  and  water  under  pressure  of  a  fluid  forced  into  the  vat, 
•  and  aftef  the  gold  and  silver  have  combined  with  the  halogen,  adding  mercury 
and  again  agitating  under  pressure  of  a  fluid  forced  into  the  vat,  next  passing  the 
ore,  mercury,  and  solution  over  amalgamated  copper  surfaces  forming  the  cathode 
of  an  electric  circuit,  and  subsequently  submitting  the  mixture  to  electrolytic 
action  between  cathodes  of  mercury  below  and  suitable  anodes  above. 

452125 — May  12,  1891.  W.  VON  SIEMENS.  Apparatus' for  extracting  metals 
from  their  ores. — The  combination  of  a  trough  for  the  flow  of  liquid,  composed 
of  numerous  sections  connected  at  alternate  ends,  with  an  inlet  at  one  end  and 
an  outlet  at  the  other,  with  two  longitudinal  shafts  in  each  section  of  the  said 
trough,  said  shaft  carrying  beaters  and  being  entirely  immersed  in  the  liquid 
contained  in  the  trough,  and  a  heating  pipe  located  below  and  between  the  said 
shafts. 

459023 — September  8,  1891.  C.  SCHREIBER  and  H.  KNUTSEN.  Process  of 
extracting  antimony  from  ores. — In  the  extraction  of  antimony  from  ore,  the  proc- 
ess which  consists  in  subjecting  the  crushed  ore  to  the  action  of  a  solution  of  sulphide 
of  sodium  and  then  precipitating  the  antimony  in  metallic  form  by  electrolysis, 
adding  hydroxide  of  sodium  to  the  solution. 

460354— September  29,  1891.  W.  VON  SIEMENS.  Apparatus  for  eUctrolytically 
separating  metals  from  ores. — In  an  electrolytical  cell,  the  combination  of  a  revolv- 
ing cathode,  a  trough-shaped  anode  situated  below  the  said  cathode,  in  the  trough 
of  which  the  cathode  revolves,  a  screen  permitting  the  passage  of  the  electrolyte 
and  of  electricity  and  capable  of  preventing  the  passage  of  vibrations  of  the  elec- 
trolyte situated  between  the  said  cathode  and  anode,  and  means  for  supplying 
•the  electrolyte  above  the  screen  and  for  withdrawing  the  oxidized  liquid  from 
the  bottom  of  the  trough  of  the  anode. 


\s 
w<^ 


PATENTS   RELATING  TO  CYANIDE  PROCESSES.  389 

473105 — April  19,  1892.  G.  J.  ATKINS.  Electrolytic  apparatus  for  separating 
gold  and  other  metals  from  their  ores. — Electrolytic  apparatus  for  separating  gold 
and  other  metals  from  their  ores,  which  consists  of  an  upright  anode  compartment 
through  which  the  ore  is  passed  continuously,  having  within  it  an  anode  constructed 
to  receive  and  retard  the  descent  of  the  ore,  while  the  ore  itself  forms  a,  more  or 
less  soluble  portion  of  such  anode  pole,  and  an  upright  cathode  compartment  and 
pole,  the  said  anode  and  cathode  compartments  communicating  through  an  open- 
ing closed  by  a  porous  diaphragm  and  having  outlets  at  their  lower  ends  for  the 
removal  of  the  ore  which  has  been  acted  upon  in  the  anode  compartment  and  of 
the  metals  and  other  substances  that  have  been  deposited  or  precipitated  in  the 
cathode  compartment. 

484869 — October  25,  1892.  G.  J.  ATKINS.  Process  of  separating  gold  and 
other  metals  from  their  ores. — The  continuous  process  of  separating  gold  and  other 
metals  from  their  ores,  which  consists  in  passing  such  ore  through  the  anode  com- 
partment of  an  electrolytic  apparatus  in  contact  with  the  anode  and  retarding 
the  descent  of  the  ore  in  the  said  anode  compartment  while  such  ore  is  kept  in  con- 
tact with  the  anode  pole  of  such  compartment,  so  as  to  form  a  more  or  less  soluble 
portion  of  such  anode  pole,  and  then  subjecting  the  ore  to  the  process  of  amalga- 
mation. 

495212 — April  11,  1893.  J.  F.  WISWELL.  Process  of  and  apparatus  for 
treating  ores. — An  improved  process  of  treating  ores  which  consists  in  submerging 
mercury  in  a  solution  of  common  salt  connecting  the  mercury  with  the  positive 
pole  of  a  generator  and  the  salt  solution  with  the  other  pole,  so  that  the  current 
will  decompose  the  salt  solution  and  cause  the  chlorine  to  be  attracted  to  the  mer- 
cury forming  calomel;  ^  treating  the  calomel  with  aqua  regia  forming  a  soluble 
mercuric  chloride,  diluting  the  latter  with  water,  treating  undecomposed  salt  solu- 
tion with  an  electric  current  to  produce  sodium  hypochlorite  and  introducing 
the  soluble  mercuric  chloride  and  sodium  hypochlorite  simultaneously  upon  the 
crushed  ore. 

495637 — April  18,  1893.  J.  PFLEGER.  Process  of  extracting  zinc  by  electrolysis. 
— The  process  of  obtaining  zinc  by  electrolysis  out  of  a  zinc-containing  anode, 
which  consists  in  adding  to  the  bath  a  basic  zinc-salt  solution  adapted  to  act  as 
electrolyte,  to  which  basic  zinc-salt  solution  a  conducting  neutral  salt  has  been 
added. 

495715 — April  18,  1893.  S.  R.  WHITALL.  Process  of  lixiviating  ores. — The 
process  of  separating  gold  and  silver  from  their  ores,  which  consists,  first,  in  roast- 
ing the  ore  to  oxidize  the  base  metals;  and,  secondly,  in  subjecting  the  roasted  ore 
to  the  action  of  a  solution  of  potassium  cyanide  and  sodium  hyposulphite,  and 
subsequently  precipitating  the  dissolved  metals;  and  the  process  of  separating 
gold  and  silver  from  siliceous  ores,  which  consists  in  subjecting  the  ore  admixed 
with  caustic  soda  and  potash  to  the  action  of  a  solution  of  potassium  cyanide  and 
sodium  hyposulphite. 

497014 — May  9,  1893.  F.  W.  CLEGHORN.  Process  of  separating  precious 
metals  from  ores. — The  process  of  separating  gold  and  silver  from  ores,  consisting 
in  filtering  through  the  ores  a  solution  of  sulphuric  acid  and  salt,  and  precipitating 
the  gold  and  silver  in  the  filtrate  solution  by  placing  metallic  iron  in  the  filtrate 
and  passing  an  electric  current  through  the  filtrate. 

501997 — July  25,  1893.  S.  H.  EMMENS.  Apparatus  for  the  electrolytic  extrac- 
tion of  metals. — In  apparatus  for  the  electrolytic  extraction  of  metals,  a  vat  having 
an  anode  lining  on  its  floor  and  sides,  in  comibnation  with  a  suitable  cathode  or 
cathodes  suspended  within  the  vat  and  a  non-porous  and  non-conducting  inner 
wall  or  curb  located  between  the  side  linings  and  the  cathode  or  cathodes  and  ex- 
tending from  the  upper  surface  of  the  floor  lining  to  above  the  surface  of  the  electro- 
lyte, and  serving  to  support  a  lining  of  the  substance  to  be  acted  upon  in  contact 
with  the  anode  side  linings  and  to  prevent  short-circuiting  between  said  anode  side 
linings  and  the  cathodes. 

507130 — October  24,  1893.  C.  HOEPFNER.  Electrolytic  production  of  metals. — 
The  process  of  obtaining  copper  and  silver  free  from  other  metals,  which  consists 
in  forming  a  cuprous-chloride  solution  of  these  metals  by  leaching  a  cupriferous 


390  APPENDIX. 

and  argentiferous  material  with  a  cupric-chloride  solution  containing  a  solvent 
for  cuprous  chloride,  separating  from  the  cuprous-chloride  solution  so  obtained 
such  metals  as  arsenic,  antimony,  cobalt,  and  the  like,  extracting  the  silver  by 
precipitation,  electrolyzing  the  cuprous-chloride  solution,  preventing  the  solution 
at  the  anode  from  commingling  with  the  solution  at  the  cathode,  mixing  together 
the  two  solutions  after  having  been  acted  upon  by  the  electric  current  and  pre- 
venting an  accumulation  of  iron  therein  by  oxidizing  and  removing  the  latter. 

512361 — January  9,  1894.  p<  C.  CHOATE.  Art  of  producing  metallic  zinc. — 
The  method  of  producing  from  an  impure  solution  of  zinc  salts  a  zinc  electrolyte 
free  from  depositable  impurities,  which  consists  in  subjecting  the  solution  to  the 
action  of  an  electric  current  to  precipitate  and  deposit  the  depositable  impurities, 
and  at  the  same  time  preventing  the  resolution  of  such  impurities  in  the  solution 
by  neutralizing  the  acid  set  free  in  the  bath  with  a  neutralizing  agent  which  is  free 
from  any  depositable  impurities  soluble  in  the  solvent  element  of  the  bath. 

512362 — January  9,  1894.  P.  C.  CHOATE.  Process  of  preparing  solutions 
carrying  salts  of  zinc.— The  process  of  forming  a  solution  carrying  salts  of  zinc, 
which  consists  in  forming  a  sulphate  solution  of  the  soluble  elements  of  the  ore 
and  recovering  the  same  therefrom  by  evaporation  and  crystallization,  heating 
the  crystallized  product  to  drive  off  the  salts  of  metals  more  volatile  than  zinc 
and  convert  those  less  volatile  than  zinc  into  compounds  insoluble  in  water  and 
finally  treating  the  mass  with  water  to  dissolve  the  zinc  element. 

518732 — April  24,  1894.  p-  C.  CHOATE.  Art  of  producing  metallic  zinc. — The 
process  of  continuously  producing  metallic  zinc  by  electrolysis,  which  consists  in 
depositing  the  zinc  from  an  acidulated  solution  of  a  zinc  salt,  drawing  off  from  the 
bath  the  free  acid  liberated  therein,  dissolving  in  such  acid  oxidized  zinc,  in  the 
state  of  fume,  freed  from  its  more  volatile  soluble  impurities,  and  returning  the 
solution  thus  formed  to  the  bath  from  time  to  time,  as  required,  to  maintain  the 
electrolyte. 

526099 — September  18,  1894.  P  DANCKWARDT.  Apparatus  for  and  process  of 
extracting  gold  or  silver  from  ores. — The  process  of  extracting  gold  and  silver  from 
ores,  which  consists  in  subjecting  the  same  simultaneously  to  the  action  of  cyanide 
of  potassium,  an  alkali  sulphide,  and  to  electrolysis;  and  the  combination  of  a. 
main  apparatus  consisting  of  a  revolving  outer  drum  having  blades,  an  insulated 
inner  drum  and  electric  connections,  with  an  auxiliary  apparatus  consisting  of  a 
series  of  communicating  tanks,  rotating  insulated  drums  and  electric  connections. 

528023 — October  23,  1894.  L-  PELATAN  and  F.  CLERICI.  Extracting  gold  from 
its  ore. — The  combination  with  a  crushing  mechanism  and  an  amalgamator,  of  a 
series  of  vessels  containing  a  solution  of  cyanide  of  potassium  and  a  salt  of  sodium, 
each  vessel  having  an  amalgamated  copper  bottom  connected  to  one  pole  of  a 
generator  of  electricity  and  a  central  shaft  having  a  zinc  pipe  and  agitator  con- 
nected to  the  other  pole,  a  filter,  a  series  of  communicating  closed  vessels  of  lead, 
each  containing  a  body  of  aluminum  chips  resting  on  a  perforated  diaphragm 
above  the  inlet  and  rising  nearly  to  the  outlet,  and  means  for  creating  a  vacuum 
beneath  the  filter  to  drive  the  fluid  through  and  into  the  series  of  lead  vessels  under 
pressure. 

531169 — December  18,  1894.  V-  ENGELHARDT.  Process  of  extracting  metals- 
from  sulphide  ores,  etc. — The  process  of  treating  the  sulphur  compounds  of  metals, 
which  compounds  have  combined  therewith  other  ore  compounds  not  soluble  in 
a  solution  of  an  alkaline  sulphydrate,  which  consists  in  extracting  the  sulphur 
compounds  by  treatment  with  an  alkaline  sulphydrate,  thereby  also  generating 
sulphureted  hydrogen,  subjecting  the  solution  thus  formed  to  the  action  of  an 
electric  current  in  the  cathode  compartment  of  an  electrolytic  cell,  in  the  anode 
compartment  of  which  is  an  alkaline  chloride,  thereby  obtaining  the  metals,  reform- 
ing the  sulphydrate,  and  liberating  free  chlorine,  treating  the  ore  residues,  result- 
ing from  the  sulphydrate  bath  with  such  chlorine,  and  subjecting  the  solution 
thus  obtained  to  the  action  of  the  sulphureted  hydrogen  first  generated  in  the  sulph- 
hydrate  bath. 

537423 — April  9,  1895.  F.  H.  LONG  and  D  C.  SKADEN.  Apparatus  for  recover- 
ing precious  metals  from  their  ores. — An  apparatus  for  recovering  precious  metals 


PATENTS  RELATING  TO    CYANIDE  PROCESSES.  391 

comprising  a  revoluble  drum,  a  perforated  metal  tube  opening  from  said  drum 
and  provided  with  a  fabric  jacket,  a  series  of  plates  secured  to  the  inner  surface 
of  the  drum  and  having  inwardly  extended  blades  or  flanges,  electric  connections 
to  the  plates  and  tube  for  rendering  the  same  of  opposite  polarity,  a  rotatable 
conveyor  located  and  working  in  said  tube  and  a  fixed  vent-pipe  passing  axially 
through  the  drumhead  and  opening  into  the  interior  of  the  drum  near  the  top 
thereof. 

538522 — April  30,  1895.  E.  D.  KENDALL.  Process  of  and  reagent  for  recover- 
ing silver  and  gold  from  solutions. — The  process  of  the  recovery  of  gold  and  silver 
from  solutions,  which  consists  of  the  following  steps:  First,  the  subjecting  of  the 
ore  containing  the  precious  metals  to  the  action  of  a  solvent,  thus  obtaining  an 
aqueous  solution  of  the  solvent  and  the  minerals  contained  in  the  ore;  second, 
subjecting  the  said  solution  to  the  electrochemical  action  of  a  mercurial  amalgam; 
third,  subjecting  the  valuable  precipitate  secured  by  the  preceding  process  to 
the  action  of  dilute  acid  in  the  presence  of  carbon;  fourth,  the  recovery  of  the 
valuable  metal  from  the  result  of  the  preceding  process. 

043546 — July  30,  1895.  E.  J.  FRASER.  Process  of  and  apparatus^  for  treat- 
ment of  precious  metals. — The  process  of  separating  gold  or  other  precious  metal 
held  in  an  electrolytic  solution,  which  consists  in  passing  the  solution  through 
a  vessel  containing  "alternating  porous  layers  of  zinc  and  carbon,  to  set  up  a  local 
voltaic  action  which  tends  to  decompose  the  solution,  precipitating  the  gold  in  the 
carbon  by  filtration. 

543673 — July  30,  1895.  M.  CRAWFORD.  Process  of  extracting  precious  metals- 
from  their  ores. — The  improved  process  of  removing  precious  metals  from  their 
ores  which  consists,  first,  in  lixiviating  the  ore  with  a  cyanide  solution  which  has 
been  subjected  to  the  action  of  an  anode  separated  from  its  corresponding  cathode 
by  a  porous  partition  which  substantially  prevents  the  circulation  of  the  electrolyte ; 
second,  in  withdrawing  said  solution  and  removing  the  precious  metals  there- 
from; third,  in  again  subjecting  the  solution  to  the  action  of  an  anode  separated 
from  its  corresponding  cathode  as  before  and  using  it  over  again  in  continuous 
rotation. 

543674 — July  30,  1895.  M.  CRAWFORD.  Process  of  extracting  precious  metals 
from  their  ores. — The  improved  process  of  extracting  precious  metals  from  their 
ores,  which  consists  in  forming  a  solution  of  a  cyanide  and  a  cyanate  of  the  cor- 
responding base,  the  total  amount  of  cyanate  being  not  less  than  25  per  cent,  of  the 
total  amount  of  cyanide  present;  lixiviating  the  ore  therewith  and  extracting 
the  dissolved  precious  metals  from  said  solution. 

543675 — July  30,  1895.  M.  CRAWFORD.  Apparatus  for  extracting  precious 
metals  from  their  ores. — An  apparatus  for  extracting  precious  metals  from  their 
ores,  which  consists  in  the  combination  of  a  tank  wherein  the  solvent  liquid  is  stored;, 
a  revoluble  lixiviating  receptacle;  a  pipe  running  from  said  storage-tank  to  the 
lixiviating  receptacle;  an  amalgamating  table;  means  for  causing  the  lixiviating 
receptacle  to  discharge  its  contents  continuously  upon  the  amalgamating  table  j 
a  separating-tank;  means  for  conducting  ore  which  has  passed  over  the  amalga- 
mating table  into  the  separating-tank;  means  for  separating  the  solid  contents'- 
of  this  separating-tank  from  its  liquid  contents;  a  third  tank;  connections  whereby 
the  solvent  liquid  thus  separated  is  passed  to  said  third  tank;  means  for 
reclaiming  the  precious  metals  from  the  solution  in  said  third  tank;  and  connec- 
tions whereby  the  solvent  liquid  is  run  from  the  third  tank  to  the  storage-tank  p 
and  a  separator  for  removing  the  tailings  of  the  ores  of  precious  metals  from  their- 
accompanying  solvent  solution,  which  consists  in  the  combination  of  a  tank  into- 
which  the  ores  and  solution  are  discharged;  a  conveyor  running  from  the  bottom, 
of  said  tank  to  a  point  exterior  thereto  by  which  the  solids  are  separated  from  the' 
liquids;  a  car-filter  with  a  permeable  bottom  situated  below  the  discharge  end 
of  the  conveyor;  and  a  second  tank  below  said  car-filter. 

544610 — August  13,  1895.  E.  W.  CLRAK.  Process  of  and  apparatus  for  extract- 
ing ores  by  electrolysis. — In  an  electric  chlorinator  for  gold  ores,  the  combination 
of  the  hollow  cylinder  constructed  in  longitudinal  sections  united  by  bands,  and 
having  the  series  of  separate  boxes  or  chambers  communicating  with  its  interior; 


392  APPENDIX. 

the  electrical  connections  consisting  of  the  anode  in  the  cylinder  chamber,  and 
the  cathodes  in  the  boxes  or  amalgamating  chambers,  the  agitator-shaft  provided 
with  the  spirally-arranged  series  of  stirrer-arms  and  adapted  to  revolve  in  the 
cylinder  chamber,  and  the  stuffing  boxes  at  the  ends  of  the  cylinder. 

546873 — September  24,  1895.  E.  A.  ASHCROFT,  Process  of  treating  zinc-bearing 
ores. — In  the  treatment  of  zinc-bearing  ores  and  zinc-bearing  products,  the  method 
of  simultaneously  depositing  zinc  from  a  catholyte  free  from  iron,  and  raising 
£i  ferrous-salt  solution  to  the  ferric  state,  which  consists  in  passing  the  zinc-bear- 
ing solution  free  from  iron,  around  the  metallic  cathodes  of  an  electrolytic  appa- 
.ratus,  and  simultaneously  passing  the  ferrous-salt  solution  around  the  insoluble 
•anodes  of  the  said  electrolytic  apparatus. 

549907 — November  19,  1895.  A.  L.  ELTONHEAD.  Apparatus  for  extracting 
gold. — In  an  apparatus  for  extracting  gold  and  other  metals,  the  combination  of 
a  mercury  receiving-box,  a  horizontally  movable  vessel  therein,  having  its  lower 
end  open  and  unobstructed  whereby  mercury  placed  within  the  box  may,  in  seek- 
ing its  level,  enter  said  vessel,  a  horizontally  placed  anode  strip  suspended  within 
the  latter,  means  for  adjusting  the  strip  vertically,  a  cathode  connection  and  con- 
ductor wires  adapted  to  connect  the  anode  and  cathode  with  a  suitable  dynamo 
or  battery. 

551648 — December  17,  1895.  L.  PELATAN  and  F,  CLERICI.  Eletcrolytic  process 
-o/  obtaining  precious  metals, — In  an  apparatus  for  the  extraction  of  precious  metals 
by  direct  electrolytic  action,  the  combination  with  an  electrolytic  vat  having 
cathodes  arranged  at  its  bottom,  of  anode  cylinders  arranged  above  the  said  cathodes, 
anode  plates  alternating  with  said  cylinders,  a  generator  of  electricity  having  its 
poles  connected  to  said  anode  cylinders  and  plates  and  to  the  cathodes,  means 
for  rotating  the  anode  cylinders  which  are  provided  with  agitators,  a  force-pump 
having  injection-pipes  to  discharge  beneath  the  anode  plates  and  cylinders,  said 
pipes  being  provided  at  or  near  their  mouths  with  interior,  concentric  rods  having 
spiral  ribs,  or  feathers,  and  suction-pipes  having  their  open  ends  arranged  above 
the  anode  plates. 

552960 — January  14,  1896.  C.  HOEPFNER.  Process  of  producing  cuprous 
oxides. — The  process  which  consists  in  leaching  cupriferous  materials  with  a  cupric- 
chloride  solution  containing  calcium  chloride,  whereby  a  solution  containing  cuprous 
chloride  is  obtained,  converting  the  cuprous  chloride  in  a  portion  of  the  solution 
into  cupric  chloride  by  means  of  a  suitable  acid  as  sulphurous  acid  in  the  presence 
•of  oxygen,  freeing  the  other  portion  of  the  solution  from  metals  other  than  cop- 
per, and  converting  the  cuprous  chloride  therein  into  cuprous  oxide  by  means  of 
a  suitable  reagent,  as  caustic  lime. 

553816 — January  28,  1896.  L.  PELATAN  and  F.  CLERICI.  Process  of  and 
apparatus  for  extracting  gold  from  its  ores. — A  single  continuous  process  for  the 
extraction  of  precious  metals  from  their  ores,  and  the  amalgamation  of  the  same 
whish  consists  in  treating  said  ores  with  a  comparatively  weak  solution  of  a  solu- 
ble cyanide,  such  as  cyanide  of  potassium,  adding  thereto  a  peroxide,  such  as 
hydrogen  binoxide,  increasing  the  electric  conductivity  of  said  solution  by  adding 
-chloride  of  sodium,  increasing  the  solvent  power  of  said  solution  by  passing  a 
relatively  weak  current  of  electricity  through  the  same,  retaining  the  sodium 
chloride  in  the  solution  practically  without  decomposition  and  continuously  revolv- 
ing the  anode  in  the  solution  over  a  fixed  cathode  of  mercury. 

556092 — March  10,  1896.  O.  FROLICH.  Process  of  extracting  noble  metals 
from  ores. — The  process  of  extracting  precious  metals  from  a  lye  containing  also 
inferior  metals,  said  lye  containing  substantially  five  grains  of  each  of  the  said 
metals  to  the  pint,  which  consists  in  subjecting  the  said  lye  to  the  action  of  an 
electric  current  of  substantially  twelve  amperes  for  each  two  square  yards  of  cathode 
surface,  whereby  the  gold  is  separated  by  electrolysis. 

563143 — June  30,  1896.  J.  DOUGLAS.  Process  of  extracting  copper  from  ores. — 
The  method  of  extracting  copper  from  solid  cuprous  chloride,  which  consists  in 
moistening  said  solid  cuprous  chloride  with  water,  inserting  both  electrodes  of  an 
electric  circuit  in  the  said  solid  cuprous  chloride,  and  then  passing  an  electric  cur- 
rent therethrough. 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  393 

56S144 — June  80,  1896.  J.  DOUGLAS.  Process  of  extracting  copper  from  ores. — 
The  process  of  extracting  copper  from  the  solid  cuprous  chloride,  which  consists  in 
suspending  the  said  solid  cuprous  chloride  in  an  acidulated  electrolyte,  inserting 
the  cathode  of  an  electric  circuit  into  the  solid  cuprous  chloride,  and  the  anode 
into  the  electrolyte,  and  passing  an  electric  current  therethrough. 

566894 — September  1,  1896.  P.  DANCKWARDT.  Apparatus  for  extracting  gold 
and  silver  from  ore. — The  combination  of  a  revolving  barrel  having  an  amalgamated 
copper  lining  with  non-conducting  bottoms,  a  series  of  inclined  perforated  metal 
strips  secured  to  such  bottoms,  insulating  rings  that  sustain  the  bodies  of  such 
strips,  and  with  electric  connections  that  communicate  with  the  barrel  and  the 
strips. 

566986— -September  1,  1896.  R.  KECK.  Cyanide  process  of  extracting  precious 
metals  from  their  ores. — The  process  of  extracting  precious  metals  from  their  ores, 
which  consists  in  dissolving  said  metals  in  a  cyanide  solution  and  extracting  them 
therefrom  by  electrolytic  precipitation  effected  by  alternating  plates  of  lead  and 
aluminum,  the  former  being  anodes  and  the  latter  cathodes. 

567503 — September  8,  1896.  L.  PELATAN  and  F.  CLERICI.  Process  of  extracting' 
gold  and  silver  from  their  ores. — The  process,  which  consists  in  submitting  the  ores 
of  gold  and  silver  to  the  action  of  a  comparatively  weak  cyanide  solution  con- 
taining chloride  of  sodium,  intensifying  the  solvent  power  of  the  solution  by  the 
passage  of  a  continuous  electric  current  having  an  electromotive  force  below 
that  required  for  the  decomposition  of  sodium  chloride  and  continuously  revolving 
the  anode  from  which  the  current  is  supplied  to  the  solution  over  a  mercury  cathode. 

568099 — September  22,  1896.  L.  PELATAN  and  F.  CLERICI.  Electrolytic  appa- 
ratus for  extracting  gold  and  silver  from  their  ores. — The  combination  with  a  vat 
having  a  flat  bottom,  of  a  cathode  of  mercury  spread  thereon,  an  anode  laving  v, 
the  form  of  an  endless  belt,  rolls  arranged  near  the  ends  of  the  vat  to  support  and 
give  continuous  movement  to  said  anode  in  parallelism  with  the  surface  of  the 
cathode,  and  means  for  imparting  continuous  movement  to  said  anode,  in  one 
direction,  it  being  provided  with  stirring  devices  moving  with  it. 

568724 — October  6,  1896.  E.  ANDREOLI.  Apparatus  for  electrodeposition  of 
gold  or  silver. — In  an  apparatus  for  the  electrodeposition  of  gold  and  silver  from 
a  solution,  a  tank  provided  with  one  or  more  anodes  and  a  series  of  amalgamated 
cathodes,  each  cathode  consisting  of  perforated,  skeleton,  or  network  plates  and 
a  layer  of  mercury  in  the  bottom  of  the  tank  into  which  each  of  the  cathodes  dips,, 
said  layer  of  mercury  being  connected  with  the  negative  pole  of  electricity,  thereby 
constituting  a  common  vehicle  for  the  current  from  all  the  cathodes  while  at  the- 
esame  time  maintaining  the  said  cathodes  constantly  amalgamated. 

568741 — October  6,  1896.  H.  R.  CASSEL.  Process  of  extracting  gold  frcm  sub- 
stances containing  it. — The  process  of  extracting  gold  from  ores,_  which  consists  in 
decomposing  a  bromide  of  an  alkaline  base  by  electrolysis,  dissolving  the  gold  \(\ 
by  the  anode  solution,  adding  the  cathode  solution,  running  the  product  through 
a  mixture  of  iron  and  carbon  to  precipitate  the  gold,  and  redecomposing  the  liber- 
ated bromine  solution  by  electrolysis. 

568843 — October  6,  1896.  V.  ENGELHARDT  and  A.  NETTEL.  Process  of  treat- 
ing metallic  sulphides, — The  process  of  treating  a  metallic  sulphur  compound,  which 
consists  in  first  converting  the  said  compound  into  a  soluble  double  sulphide  by 
treating  it  with  any  suitable  reagent,  such  as  the  sulphydrate  of  calcium  in  aque- 
ous solution;  then  decomposing  the  resulting  solution  by  electrolysis  to  produce 
the  metal  and  sulphureted-hydrogen  gas,  then  treating  the  spent  solution  with 
carbonic-acid  gas  to  precipitate  a  carbonate  of  the  base  and  liberates  ulphureted- 
hydrogen  gas,  then  recovering  the  oxide  of  the  reagent  and  the  carbon ir-aoid 
gas  from  the  precipitate  by  calcination,  then  combining  the  sulphureted-ln  drogen 
gas  given  off  during  the  process  with  the  said  oxide  to  form  more  reagent,  and 
using  the  recovered  carbonic-acid  gas  to  treat  more  spent  solution. 

571468 — November  17,  1896.  T.  P.  BARBOUR.  Process  of  treating  ores. — The 
process  of  treating  ores,  which  consists  in  first  treating  the  raw  material  with 
copper  oxide  and  sulphuric  acid,  then  chlorinating  the  pulp  thus  treated,  intro- 
ducing the  chlorinated  mass  into  a  suitable  agitator  having  zmc  therein,  and  estab- 
lishing an  electric  current  through  the  mass  in  the  presence  of  zinc;  and  a  chlor- 


^ 


394  APPENDIX. 

inating-tank  for  treating  ores  consisting  of  a  revoluble  cask  having  a  single  man- 
hole and  a  circular  series  of  bungholes,  copper  pole  disks  secured  within  the  cask 
at  opposite  ends  thereof  and  arranged  in  an  electric  circuit,  insulator  bracing 
p_osts  arranged  between  said  disks  and  the  outer  heads  of  the  tank,  flanged  guide- 
rings  encircling  said  cask  at  an  intermediate  point,  spur-rings  encircling  the  cask 
.near  its  opposite  ends,  and  a  horizontal  drive-shaft  carrying  guide-rolls  engaging 
.said  flanged  guide-rings  and  drive-pinions  engaging  said  spur-rings. 

573233 — December  15,  1896.  M.  NETTO.  Process  of  precipitating  precious 
metals  from  their  alkali-cyanide  solutions. — The  process  of  precipitating  silver  and 
gold  from  their  alkali-cyanide  solutions,  which  consists  in  acidulating  the  alkali- 
cyanide  solution  containing  said  metals  with  hydrochloric  acid  so  as  to  precipi- 
tate silver  chloride,  separating  said  silver  chloride  by  filtration,  subjecting  the 
acid  filtrate  to  the  action  of  the  electric  current  so  as  to  deposit  the  gold  on  the 
cathode,  and  regenerating  the  cyanide  solution  by  the  addition  of  caustic  alkali. 

578171— March  2,  1897.  C.  T.  TURNER.  Electrolijtical  apparatus  .—An  elec- 
trolytic apparatus,  provided  with  an  anode  consisting  of  a  non-conducting  recep- 
tacle coated  with  an  anti-corrosive  substance  and  provided  with  an  outer  coat- 
ing of  a  conducting  material  and  means  for  connecting  said  outer  coating  with 
the  positive  pole  of  a  source  of  electrical  supply. 

579872— March  30,  1897.  J.  H.  HAYCRAFT.  Process  of  treating  auriferous 
and  argentiferous  ores. — The  process  of  treating  ores  consisting  in  introducing 
the  ore  into  a  pan,  adding  thereto  mercury  and  soluble  salts  capable  of  yielding 
chlorine  by  electrolysis,  raising  the  ore  contents  of  the  pan  to  about  the  boiling- 
point  of  water  and  passing  a  current  of  electricity  through  the  heated  mass  while 
stirring  the  same  to  secure  a  simultaneous  electrolytic  chlorination  and  electro- 
amalgamation,  and  maintaining  the  anode  out  of  vertical  alignment  with  the 
mercury  cathode. 

581160 — April  20,  1897.  H.  HIRSCHING.  Process  of  treating  ores  containing 
silver  and  gold. — The  process  of  treating  ores,  which  consists  in  subjecting  them 
in  the  presence  of  moisture  to  the  action  of  ammonia  and  a  nitrate,  and  then  pre- 
cipitating the  metal  or  metals  from  the  resulting  solution. 

582077 — May  4,  1897.  E.  MOTZ.  Apparatus  for  extracting  precious  metals. — 
In  an  apparatus  for  extracting  precious  metals,  the  combination  of  a  rotative 
drum  provided  with  a  manhole  and  having  a  valved  connection  for  the  admission 
of  compressed  air,  a  core  of  insulating  material  mounted  to  turn  in  the  said  drum, 
metal  plates  forming  the  positive  and  negative  electrodes  of  an  electric  circuit 
and  arranged  respectively  on  the  drum  and  core,  and  an  electrical  connection 
for  said  plates  on  the  core,  the  said  connection  being  arranged  to  lock  the  drum 
and  core  together. 

584242 — June  8,  1897.  P.  G.  SALOM.  Process  of  making  commercial  lead 
from  lead  ore. — The  process  of  converting  lead  ore  into  commercial  lead,  without 
the  application  of  heat,  by  subjecting  the  ore  to  the  action  of  nascent  hydrogen, 
electrolytically  developed,  producing  thereby  a  spongy  mass,  and  afterward,  while 
the  mass  is  in  a  non-oxidized  condition,  applying  a  consolidating  pressure. 

685355 — June  29,  1897.  C.  A.  BURGHARDT  and  G.  RIGG.  Process  of  obtain- 
ing metallic  zinc  and  copper  from  ores. — The  improved  process  of  recovering  metallic 
zinc  and  metallic  copper  from  cuprous  zinc  ore,  which  consists  in  treating  the  roasted 
and  ground  ores  with  an  ammoniacal  solution,  then  in  freeing  the  resultant  liquid 
from  iron  dissolved  by  said  solution,  then  in  depositing  the  metallic  copper  on 
suitable  metallic  plates  acting  as  a  couple,  and  in  finally  effecting  the  electrolytic 
deposition  of  the  metallic  zinc. 

585492 — June  29,  1897.  J.  F.  WEBB.  Method  of  an  apparatus  for  separating 
precious  metals  from  their  solvent  solutions. — The  improved  method  of  separating 
precious  metals  from  a  solvent  solution  containing  the  same,  consisting  in  passing 
the  solution  alternately  through  a  body  of  carbon  and  zinc,  and  subjecting  the 
same  in  its  passage  to  an  air  current;  and  a  metallurgical  filter  for  this  purpose 
vcontaining  the  same,  consisting  of  a  series  of  alternate  compartments,  or  recep- 
tacles, containing,  respectively,  carbon  and  zinc,  through  which  the.  solvent  solu- 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  395 

tion  is  passed  with  an  upward  and  downward  flow,  and  electric  circuit  completing 
connection  between  the  zinc  and  carbon. 

588076 — August  10,  1897.  B.  MOHR.  Process  of  treating  sulphide  ore. — The 
process  for  treating  sulphide  ore  by  acting  on  the  pulverized  ore  with  acid  sodium 
or  potassium  sulphate,  so  as  to  obtain  a  solution  of  sulphate  of  zinc,  depositing 
the  zinc  by  electrolysis  and  thus  recovering  the  acid  alkali  sulphate,  and  treating 
the  insoluble  residue  obtained  by  the  lixiviation  for  recovery  of  the  other  metals. 

588740 — August  24,  1897.  B.  BECKER.  Apparatus  for  treating  gold  and  silver 
ores. — In  apparatus  for  the  treatment  of  gold  and  silver  ores  the  combination 
of  a  vat  provided  with  amalgamating  plates  and  adapted  to  contain  cyanide  of 
potassium,  in  solution,  and  the  ore  to  be  treated,  a  vat  containing  the  electrodes 
of  an  electrolytic  apparatus  and  means  for  causing  the  circulation  of  the  cyanide 
of  potassium  solution  through  the  amalgamating  vat,  and  for  distributing  it  in 
the  electrolytic  vat. 

590801 — September  28, 1897.  W.  L.  BROWN.  Process  of  treating  rebellious  ores. — 
The  process  of  treating  ores  finely  divided  and  mixed  with  water,  which  consists 
in  adding  a  suitable  compound  to  said  ores  and  water,  which  compound  contains 
an  element  which  has  a  chemical  affinity  for  the  base  constituents  of  the  ore,  then 
passing  an  electric  current  through  said  material  to  unite  the  said  element  chem- 
ically  with  the  base  constituents  and  to  liberate  the  precious  metals,  then  cir- 
culating the  material  over  an  amalgamated  surface  which  is  not  in  the  electrical 
circuit,  and  finally  returning  the  material  again  through  the  field  of  electrolytic 
action. 

592055 — October  19,  1897.  E.  C.  KETCHUM.  Process  of  treating  ores. — The 
process  of  treating  mixed  sulphide  ores  containing  lead  and  zinc,  which  consists 
in  first  roasting  the  ores,  then  subjecting  the  roasted  ores  to  the  action  of  a  solu- 
tion of  caustic  alkali  in  the  presence  of  heat  to  remove  from  the  ores  the  lead  and 
the  zinc,  then  subjecting  the  caustic  solution  containing  the  lead  and  zinc  to 
electrolytic  action  in  one  or  more  cells  to  remove  the  lead,  the  anodes  of  which 
cells  are  immersed  in  a  volume  of  pure  caustic  solution,  which  is  separated 
by  a  porous  medium  from  the  electrolyte  containing  the  lead  and  zinc,  and  then 
subjecting  the  caustic  solution  or  electrolyte  containing  the  zinc  only  to  electrolytic 
action  in  one  or  more  cells  to  remove  the  zinc. 

592973 — November  2,  1897.  E.  MOTZ.  Electrolytic  apparatus. — In  an  elec- 
trolytic apparatus  the  combination  with  a  frame  or  sluice  of  a  series  of  convex 
cathode  plates  located  in  the  bottom  of  said  frame  or  sluice,  a  series  of  anode  plates 
having  curved  under  faces  and  disposed  above  said  cathode  plates,  blocks  secured 
to  the  anode  plates  and  supported  in  the  frame  or  sluice,  each  block  having  a  recess 
in  its  upper  edge,  a  series  of  conductors  connected  with  said  anode  plates  and 
terminating  in  said  recesses  in. the  blocks,  a  conducting  rod  disposed  in  said  recesses 
on  the  first-mentioned  conductors  and  having  a  notch  therein,  a  cross-bar  passing 
through  said  notch,  a  conductor  with  which  said  cross-bar  is  electrically  connected, 
locking  devices  for  securing  the  cross-bar  to  the  frame  or  sluice,  and  a  conductor 
connected  with  the  cathode  plates. 

594611 — November  30,  1897.  S.  H.  EMMENS.  Process  of  and  apparatus  for 
removing^  zinc  from  zinciferous  ores. — The  process  of  treating  zinciferous  ores,  which 
consists  in  pulverizing  and  roasting  the  ore,  leaching  it  in  a  series  of  vessels  through 
which  the  solution  flows  continuously,  and  subjecting  the  contents  of  each  vessel 
intermittently  to  electrolytic  action,  whereby  the  solution  is  rendered  alternately 
acid  and  neutral  or  more  acid  and  less  acid  in  contact  with  each  body  of  ore;  and 
an  apparatus  for  treating  zinciferous  ores,  comprising  a  series  of  leaching-vats, 
each  provided  with  an  inlet-pipe  extending  to  the  bottom  and  with  an  exit-pipe 
or  trough  leading  from  the  top  of  the  vat,  and  each  provided  at  bottom  with  an 
insoluble  anode,  a  series  of  movable  cathodes  suspended  above  said  vats,  means 
for  raising  and  lowering  the  cathodes  of  adjoining  vats  alternately,  and  an  electric 
circuit  to  the  respective  poles  with  which  said  anodes  and  cathodes  are  connected. 

597820 — January  25,  1898.  N.  S.  KEITH.  Art  of  obtaining  gold  and  silver 
from  auriferous  and  argentiferous  materials. — The  process  of  obtaining  a  precious 
metal  from  its  ores,  which  consists  first  in  dissolving  the  gold  or  silver  in  a  cyanide 
solution  containing  cyanide  of  mercury  and  free  cyanide  of  an  alkaline  metal,  such 


396  APPENDIX. 

as  cyanide  of  potassium,  and  then  passing  a  current  of  electricity  through  said 
solution  to  a  metallic  cathode,  whereby  an  easily  removable  layer  of  the  precious 
metal  and  mercury  is  simultaneously  deposited  upon  said  cathode. 

598193 — February  1,  1898.  E.  ANDREOLI.  Apparatus  for  electrodeposition  of 
gold  and  silver. — In  apparatus  for  the  electrodeposition  of  gold,  silver,  or  other 
metals,  anodes  of  peroxidized  lead  acting  in  the  presence  of  and  in  combination 
with  a  cyanide  or  cyanide-compound  solution. 

600351 — March  8,  1898.  E;  A.  ASHCROFT.  Treatment  of  metalliferous  ores 
and  products. — The  improved  process  of  preparing  a  solution  suitable  for  leaching 
zinc-bearing  ores  of  zinc-bearing  products,  consisting  in  electrolyzing  a  zinc-bear- 
ing solution  successively  in  contact  with  a  suitable  cathode  and  an  anode  result- 
ing from  the  preliminary  furnace  treatment  of  products  or  ores  containing  cop- 
per and  iron,  and  then  depositing  the  copper  from  the  resulting  ferrous  solution, 
and  simultaneously  raising  the  iron  content  of  such  solution  to  the  ferric  state 
by  electrolyzing  the  said  resulting  ferrous  solution  successively  in  contact  with 
suitable  cathodes  and  insoluble  anodes. 

601068 — March  22,  1898.  F.  W.  WHITRIDGE.  Method  of  and  apparatus  for 
extracting  gold  from  its  ores. — The  method  of  extracting  gold  from  a  weak  cyanide 
solution,  which  consists  in  circulating  the  solution  over  anodes  of  iron  and  cathodes 
of  lead,  said  cathodes  being  formed  of  thin  plates  arranged  at  short  distances  apart 
and  having  from  9  to  10  square  meters  of  surface  for  each  ton  of  solution  in  con- 
tact with  them;  and  subjecting  the  said  solution  while  in  motion  to  an  electric 
current  of  from  3.5  to  4  volts,  and  of  from  0.5  to  1.5  amperes  per  square  meter 
of  cathode  surface;  and  in  apparatus  for^  obtaining  gold  from  a  weak  cyanide 
solution  by  electrolysis,  the  combination  with  a  cell  provided  with  anodes  of  iron 
and  cathodes  of  lead  formed  of  thin  plates,  said  cathode  plates  having  from  9  to 
10  square  meters  of  surface  to  each  ton  of  solution  in  the  cell;  of  means  for  cir- 
culating the  solution  in  the  cell,  and  means  for  subjecting  the  solution  to  a  weak 
current  of  electricity. 

60390 1£ — May  10,  1898.  J.  R.  HEBAUS.  Apparatus  for  extracting  precious 
metals. — An  apparatus  for  extracting  precious  metals  from  their  ores,  comprising 
a  tank  having  an  amalgamated  copper  lining  forming  a  cathode  and  a  multiplicity 
of  agitators,  each  rotating  on  its  own  axis  and  at  the  same  time  traveling  around 
the  tank,  the  said  agitators  forming  an  anode  and  an  electric  circuit. 

605835 — June  21,  1898.  E.  and  G.  ANDREOLI.  Electrolytic  production  of  amal- 
gams, etc. — An  apparatus  for  the  production  of  amalgam,  consisting  of  a  cell  pro- 
vided with  positive  and  negative  compartments  separated  by  porous  diaphragms, 
the  negative  compartments  having  a  raised  middle  portion  in  the  form  of  a  table 
or  block  between  the  sides  of  which  and  the  said  partitions  are  narrow  vertical 
spaces,  the  top  of  the  block  or  table  and  the  vertical  spaces  being  covered  and 
filled  with  a  continuous  body  of  mercury  forming  a  cathode. 

614572 — November  22,  1898.  J.  C.  McNuLTY.  Method  of  and  apparatus  for 
treating  ores. — The  art  of  extracting  precious  metals  from  their  ores,  consisting 
in  mixing  pulverized  ore  with  an  electrolytic  fluid,  causing  the  mixture  to  flow 
from  one  level  to  another  between  adjacent  electrode  plates  of  opposite  polarity, 
passing  an  electric  current  between  said  plates  and  vibrating  the  electrodes  in  a 
direction  substantially  at  right  angles  to  the  plane  of  said  electrodes  for  the  pur- 
pose of  preventing  the  polarization  thereof;  and  in  apparatus  for  the  electro- 
lytic treatment  of  ores  the  combination  of  a  plurality  of  vats  arranged  in 
pairs  communicating  at  the  top,  adjacent  electrode  plates  of  opposite  polarity 
suspended  within  said  vats  and  connected  with  a  source  of  electricity,  vibratory 
supports  for  said  electrodes,  means  for  vibrating  the  same  at  substantially  right 
angles  to  their  planes,  a  pressure  conduit  for  pulp  leading  to  the  bottom  of  the 
first  vat  to  provide  an  upward  current  therethrough,  and  an  exit  at  the  bottom 
of  the  succeeding  vat  providing  a  discharge  for  the  downward  current  of  pulp 
overflowing  from  the  top  of  the  vat  preceding. 

616891 — January  3,  1899.  G.  D.  BURTON.  Electrolytic  apparatus  for  treating 
metals  and  ores. — In  an  electrolytic  ore-treating  apparatus,  the  combination  of  a 
tank  for  containing  an  electrolyte,  an  anode  disposed  in  said  tank,  a  cathode  dis- 


PATENTS  RELATING  TO  CYANIDE   PROCESSES.  397 

posed  in  said  tank,  a  screen  or  deflector  also  disposed  in  said  tank  between  the 
anode  and  cathode  and  adapted  to  distribute  the  ore  or  material  being  treated, 
said  screen  having  a  conductive  surface  connected  to  the  negative  pole  of  an  elec- 
tric source  whereby  it  is  adapted  to  collect  a  portion  of  the  product  reduced  from 
the  ore  by  the  action  of  the  current  and  the  electrolyte. 

617911 — January  17,  1899.  E.  A.  SMITH  and  M.  H.  LYNG.  Method  of  extract- 
ing metallic  ores.— The  wet  process  of  extracting  copper  from  its  ores  having  pre- 
cious metal  therein,  which  consists  in  digesting  the  pulverized  ore  under  action 
of  heat  and  an  oxidizing  agent,  in  presence  of  sulphuric  acid,  exposing  the  dis- 
solved sulphates  to  metallic  copper  for  precipitation  of  the  silver,  treating  the 
filtrate  electrolytically  to  deposit  the  copper,  evaporating  the  lean  electrolyte  to 
concentrate  the  free  acid,  and  crystallize  the  metallic  sulphates,  and  finally  cal- 
cining such  crystallized  sulphates  to  properly  regenerate  them  as  oxidizing  agents 
for  reuse. 

623822 — April  25,  1899.  L.  PELATAN.  Apparatus  for  treating  ores  or  the 
like. — In  apparatus,  the  combination  with  a  circular  vat,  of  a  revolving  anode, 
situated  above  and  parallel  to  a  mercury  cathode,  with  an  unobstructed  space 
above  the  surface  of  the  cathode,  the  said  anode  having  arms  which  extend  close 
to  the  peripheral  wall  of  the  vat  and  are  suspended  from  a  shaft,  and  are  pro- 
vided with  pins  or  stirrers  projecting  upward  and  downward  to  within  a  short 
distance  of  the  underlying  cathode,  and  projections  or  baffles  extending  inwardly 
from  the  inner  surface  of  the  peripheral  wall  of  the  vat. 

626972 — June  13,  1899.  T.  CRANE Y.  Electrolytic  apparatus  for  deposition 
of  metals  from  solution. — In  an  electrolytic  apparatus,  the  combination  of  an  outer 
tank  provided  with  suitable  feed  and  discharge  connections  for  the  liquid  into 
the  bottom  and  top,  respectively,  and  an  electrolytic  couple,  composed  of  sheet 
or  analogous  electrodes  each  folded  in  a  fabric,  with  oppositely  projecting  mar- 
ginal portions  and  rolled  together  into  a  tight  bundle  and  sealed  in  the  tank,  whereby 
the  fabric  inclosing  the  electrode  forms  a  porous  medium  through  which  the  elec- 
trode is  compelled  to  flow. 

627442— June  20,  1899.     L.  PELATAN.     Process  of  electrolytically  treating  ores. — 
The  improvement  in  processes  of  treating  ores  electrolytically,  consisting  in  add-      ^>y* 
ing  to  a  sludge,  consisting  of  ore  and  water,  a  solvent  and  picric  acid  as  an  oxi- 
dizing agent  and  then  passing  an  electric  current  therethrough. 

631040 — August  15,  1899.  J.  E.  GREEN AWALT.  Process  of  extracting  precious 
metals  from  their  ores. — -A  process  for  the  treatment  of  gold  and  silver  ores  which 
consists,  first,  in  properly  roasting  the  pulverized  ore;  second,  placing  the  ore  Jf 
in  a  filtering-vat;  third,  washing  the  ore  to  remove  soluble  salts;  fourth,  in  pass-  (T) 
ing  through  the  ore  an  electrolyzed  solution  consisting  of  a  solution  of  chlorides — • 
chiefly  sodium  and  ferric  chlorides — with  a  small  percentage  of  bromides  and 
small  quantities  of  chlorine,  bromine,  and  hypochlorous  acid,  with  such  other 
compounds  as  result  from  the  electrolysis  of  a  chloride  and  bromide  solution;  fifth, 
passing  the  solution  after  it  leaves  the  ore  through  a  precipitating-tank ;  sixth, 
passing  the  solution  after  it  leaves  the  precipitating-tank  through  the  positive 
or  onode  compartment  of  an  electrolytic  cell,  keeping  the  solution  separate  and 
distinct  from  the  solution  in  the  negative  or  cathode  compartment  of  the  cell; 
and,  seventh,  returning  the  solution  from  the  regenerating  cell  to  the  ore  in  the 
vat  and  passing  it  thence  to  the  precipitating-tank,  again  to  the  regenerating  cell, 
arid  again  to  the  ore  as  often  as  may  be  required  to  effect  the  necessary  saving 
of  the  values. 

633544 — September  19,  1899.  H.  S.  BADGER.  Electrolytic  apparatus  for  pre- 
cipitating metals. — A  precipitating-tank  comprising  the  tank  body,  having  a  mer- 
cury-coated surface  in  its  bottom,  a  re  voluble  shaft  suspended  in  the  tank  and 
provided  with  hollow  arms  having  perforations  on  their  lower  sides  to  deliver 
air  or  vapor  in  proximity  to  the  said  surface,  means  for  rotating  the  revoluble 
devices,  means  for  introducing  air  or  vapor  to  the  hollow  arms,  and  an  electric 
circuit  in  which  the  shaft,  agitating  arms,  and  mercury-coated  surface  are  located. 

639766 — December  26,  1899.  L.  E.  PORTER.  Apparatus  for  extracting  precious 
metals  from  ores. — The  combination  of  a  rotatable  barrel  adapted  to  form  the 


398  APPENDIX. 

cathode;  a  porous  lining  of  non-conducting  material  arranged  inside  the  barrel; 
a  lining  of  filtering  material  arranged  inside  the  non-conducting  lining;  anode 
plates  arranged  inside  the  filter  lining;  a  source  of  electrical  energy,  having  one 
pole  connected  with  the  barrel  and  the  other  pole  connected  with  the  anode  plates. 
640718 — -January  2,  1900.  C.  P.  TATRO  and  G.  DELIUS.  Process  of  extracting 
precious  metals. — In  the  process  of  separating  precious  metals  from  ores,  the  steps 
comprising  electrolytically  depositing  a  portion  of  the  precious  metals  in  the  bath 
upon  a  drum  cathode  revolving  partially  immersed  in  the  bath,  at  the  same  time 
scraping  the  said  deposit  from  the  drum,  also  simultaneously  depositing  other 
portions  of  similar  precious  metals  in  the  same  bath  upon  a  cathode  of  sodium 
amalgam. 

641571 — January  16,  1900.  W.  WITTER.  Process  of  producing  solution  of 
cyanogen  halide. — The  process  for  producing  a  solution  of  cyanogen  halide  by 
electrolyzing  in  a  bath  without  a  diaphragm  and  with  inert  electrodes  a  solution 
containing  an  alkali  cyanide,  an  alkali  halide,  and  the  salt  of' a  metal  which  forms 
an  insoluble  hydroxide. 

649151 — May  8,  1900.  W.  WRIGHT.  Apparatus  for  extracting  metals  from 
refractory  ores. — An  apparatus  for  extracting  metals  from  refractory  ores,  com- 
prising a  tank  for  receiving  a  sludge  of  such  ores;  a  stationary,  horizontal  per- 
forated partition  in  said  tank,  fcrming  beneath  it  a  chamber;  a  cathode  on  the 
bottom  of  the  tank  within  said  chamber;  a  filtering  medium  carried  on  the  par- 
tition; a  number  of  pins  arranged  in  a  series  of  concentric  circles  projecting  upward 
from  said  partition;  a  main  driving-shaft;  a  series  of  radial  arms  supported  by 
said  shaft,  and  a  plurality  of  anodes  carried  by  said  arms  and  working  between 
the  series  of  concentric  pins. 

650646 — May  29,  1900.  F.  H.  LONG.  ^  Apparatus  for  electrolytic  reduction  of 
ores. — An  electrolytic  apparatus,  the  combination  with  a  reducer  vessel;  its  bot- 
tom cathode  and  a  diaphragm  above  said  cathode,  of  a  set  of  dependent  anodes, 
each  consisting  of  a  carbon  head;  a  copper  stem  extended  therefrom  through 
the  vessel;  an  incasing  iron  tube  carried  by  the  vessel  head  to  sustain  the  anode 
pole;  a  vulcanite  sheath  for  said  tube,  and  suitable  elastic  gaskets  to  expansively 
close  the  joints. 

653538 — July  10,  1900.  N.  L.  TURNER.  Electrolytic  apparatus. — An  electro- 
lytical  apparatus,  comprising  a  tank,  rotary  agitators  located  therein  eccentrically, 
a  series  of  electrodes  whose  main  portion  is  concentric  with  the  tank,  while  the 
portions  adjacent  to  the  agitators  are  curved  concentrically  with  the  axes  of  said 
agitators,  and  electrodes  of  opposite  polarity  to  those  first  named. 

654437 — July  24,  1900.  W.  A.  CALDECOTT.  Method  of  extracting  gold  from 
cyanide  solutions  containing  the  preciou.s  metals. — Means  for  extracting  gold  from 
cyanide  solutions  in  depositing  cells,  consisting  in  a  mechanical  mixture  of  zinc 
shavings  and  lead  shavings. 

656305 — August  21,  1900.  W.  STRZODA.  Process  of  electrolytically  extracting 
zinc  from  ores. — The  process  of  electrolytically  extracting  zinc  from  its  ores,  which 
consists  in  placing  the  disintegrated  or  pulverized  ore  in  its  natural  state  in  an 
electrolytic  vat  containing  an  aqueous  alkali-metal  solution  capable  of  dissolving 
the  cre^  with  production  of  a  zincate  and  in  direct  contact  with  the  cathode,  and 
closing  the  circuit  through  the  vat,  thereby  precipitating  zinc  and  the  alkali  metal 
at  the  cathode,  the  alkali  metal  reacting  with  the  water  to  regenerate  the  solvent 
solution. 

657032 — August  28,  1900.  A.  M.  ROUSE.  Apparatus  for  electrolyzing  ores. — 
In  an  apparatus  of  the  class  described  having  an  anode  and  a  cathode  suitably 
arranged  therein,  the  combination  of  a  tank  having  an  outer  compartment,  a 
tube  located  therein  having  an  open  upper  end  and  provided  at  its  lower  end  with 
openings  forming  communication  from  said  compartment,  a  driving-shaft  pro- 
jecting within  said  tube,  an  inner  cup  carried  by  said  shaft,  wings  carried  by  said 
cup,  an  outer  cup  carried  by  said  wings,  a  discharge  duct,  and  a  valve  arranged 
to  close  said  duct. 

662286 — November  20,  1900.  E.  MOTZ.  Electrolytic  apparatus. — In  an  elec- 
trolytic cell  having  open  ends,  the  combination  with  a  removable  cross-bar  and 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.  399 

means  for  supporting  it  in  position,  of  a  metallic  plate  covering  the  bottom  and 
two  sides  of  the  bar,  and  forming  the  anode  plate  of  the  cell,  of  a  metallic  plate 
arranged  horizontally  below  and  parallel  with  the  bottom  of  the  cross-bar,  so  as 
to  form  a  passage  between  such  plate  and  the  bottom  of  the  cross-bar,  suc^i  plate 
forming  a  cathode  plate  of  the  cell,  and  an  auxiliary  metallic  cathode  plate  arranged 
vertically  and  parallel  with  the  sides  of  the  cross-bar  and  in  circuit  with  the  hori- 
zontal cathode  plate,  such  vertically  arranged  plate  extending  below  the  plane 
of  the  bottom  of  the  cross-bar,  so  as  to  more  or  less  obstruct  the  said  passage. 

664537 — December  25,  1900.  J.  DOUGLAS.  Process  of  extracting  copper. — The 
process  of  reducing  copper  ore  and  matte,  which  consists  in  electrolyzing  solid 
cuprous  chloride,  employing  the  gases  evolved  in  the  treatment  of  copper  ore  and 
matte,  employing  the  electrolyte  resulting  from  the  electrolyzing  of  the  solid  cu- 
prous chloride  as  a  solvent  for  the  cuprous  chloride  so  produced,  and  recovering 
the  copper  from  the  solution  by  electrolysis. 

668842— February  26,  1901.  A.  M.  ROUSE.  Apparatus  for  electrolytically 
extracting  and  depositing  gold  and  silver  from  their  ores. — In  an  apparatus,  the  com- 
bination of  a  series  of  pulp-receiving  tubs,  anodes  and  cathodes  arranged  in  said 
tubs,  an  agitation-tube  having  communication  with  said  tubs  at  their  upper  and 
lower  ends,  an  agitator  arranged  in  said  tube,  perforated  conduits  located  in  the 
upper  ends  of  said  tubs,  chutes  located  beneath  said  conduits  onto  which  the  ore 
pulp  is  discharged,  and  deflectors  located  beside  said  conduits  adapted  to  direct 
the  flow  of  pulp  onto  said  chutes  as  it  passes  through  said  conduits. 

669752— March  12,  1901.  P.  W.  KNAUF.  Electrolytic  apparatus. — An  element 
for  an  electrolytic  series,  consisting  of  a  metallic  receptacle  having  its  lower  por- 
tion of  less  diameter  than  the  upper  portion  and  having  a  bottom  surface  which 
is  inclined  upward  radially  from  the  center  to  the  outer  periphery,  in  combination 
with  an  exterior  peripheral  seat  arranged  below  the  upper  edge,  and  an  orifice 
adjacent  to  said  seat. 

669926 — March  12,  1901.  C.  HOEPFNER.  Process  of  electrolytical  extraction 
of  metals. — A  process  which  consists  in  placing  a  soluble  metallic  anode  in  a  solu- 
tion capable  of  dissolving  the  same,  placing  a  suitable  cathode  in  a  second  similar 
solution  containing  a  metal  more  electropositive  than  that  of  the  anode,  inter- 
posing a  third  similar  solution  of  less  solution  pressure  between  the  two  first  men- 
tioned, placing  an  auxiliary  cathode  therein,  separating  the  solutions  by  suitable 
diaphragms,  maintaining  the  solutions  in  motion  and  at  a  temperature  above 
normal,  passing  a  current,  thereby  dissolving  the  anode  and  precipitating  the 
cathode  metal  at  the  cathode,  and  part  of  the  diffused  anode  metal  at  the  aux- 
iliary cathode,  precipitating  the  anode  metal  from  the  anode  and  intermediate 
solutions  and  returning  the  resulting  solution  when  enriched  in  cathode  metal 
to  the  cathode  cell. 

678526 — July  16,  1901.  C.  P.  STEWART.  Apparatus  for  the  recovery  of  gold 
from  cyanide  solutions. — An  apparatus  for  recovering  precious  metals  from  flowing 
cyanide  solutions,  comprising  in  combination  a  relatively  long  substantially  hori- 
zontal trough,  means  for  supplying  the  solution  at  one  end  thereof,  a  partition 
near  the  receiving  end  of  the  trough  for  distributing  the  solution,  a  retaining 
partition  at  the  discharge  end  of  the  trough  adapted  to  retain  the  solution  in  the 
trough  to  the  desired  height,  a  body  of  quicksilver  in  the  bottom  of  the  trough 
between  said  partitions,  a  series  of  transverse  anode  supports  extending  substan- 
tially from  partition  to  partition,  a  series  of  anodes  adjustably  mounted  in  said 
supports  and  extending  down  into  the  path  of  the  flowing  solution,  and  suitable 
electric  connections. 

682155 — September  3,  1901.  C.  P.  TATRO  and  G.  DELIUS.  Electrolytic  appa- 
ratus for  extracting  precious  metals. — In  apparatus  for  extracting  precious  metals, 
a  tub:  a  mercurial  cathode  in  the  bottom  thereof,  a  principal  anode,  means  for 
lowering  it  into  and  raising  it  out  of  the  tub,  and  a  minor  anode  permanently  in 
the  tub. 

689018 — December  17,  1901.  W.  ORR.  Method  of  recovering  cyanides. — The 
method  of  regenerating  cyanide  solutions  which  have  become  fouled  by  the  pres- 
ence of  zinc  and  copper  contained  in  the  solutions,  as  double  cyanide  of  zinc  and 


400  APPENDIX. 

copper  with  the  alkaline  metals  which  consists,  first,  in  passing  through  the  solu- 
tion from  a  series  of  zinc  anodes  to  a  corresponding  series  of  metallic  cathodes 
a  current  of  electricity;  next,  in  introducing  into  such  solution  alkaline  hydrate, 
being  hydrate  of  the  monovalent  alkali  metals  and  hydrate  of  the  divalent  alkali 
metals  in  the  proportion  of  about  two  to  one;  next  introducing  into  the  solution 
a  soluble  alkali -metal  sulphide,  and  finally  removing  the  resulting  zinc-sulphide 
precipitate. 

689674 — December  ?4i  1901.  A.  I.  IRWIN.  Machine  for  extracting  metal  from 
ores. — In  a  machine  for  the  automatic  and  continuous  extraction  and  deposition 
of  metal  from  ores  at  one  and  the  same  time,  a  treatment-tank,  an  endless  anode 
traveling  in  s?id  tank,  the  upper  and  lower  stretches  of  the  anode  being  in  posi- 
tion to  be  immersed  in  the  solution  in  the  tank,  diagonally  disposed  blocks  of 
insulating  material  attached  to  said  anode,  cathodes  in  the  tank,  one  under  each 
stretch  of  trie  anode,  and  connections  with  a  source  of  electricity. 

689959 — December  31,  1901.  E.  L.  GRAHAM.  Process  of  disintegrating  and 
comm,invting  minerals  or  ores. — The  process  of  treating  ores,  consisting  of  the  fol- 
lowing steps:  First,  immersing  the  ores  in  a  solution  of  sulphuric  and  hydrofluoric 
acids  incapable  of  dissolving  the  ore;  second,  passing  an  electric  current  of  suffi- 
cient strength  to  disintegrate  the  ore  through  the  solution;  and  third,  extracting 
the  metal  from  the  ore. 

699964 — May  13,  1902.  F.  H.  LONG.  Electrolytic  converter. — In  electrolytic 
converters,  the  combination  with  the  closed  reducer  vessel  having  the  anode  and 
cathode  terminals  and  the'  interposed  diaphragm  dividing  the  vessel  into  upper 
anode  and  lower  cathode  chambers,  of  a  combined  separator  and  vent-pipe  conT 
nected  to  the  cathode  chamber  beneath  the  diaphragm  extending  upwardiy  above 
the  level  of  said  diaphragm  and  having  a  free  outlet  for  the  gases. 

700941— May  27,  1902.  N.  S.  KEITH.  Process  of  treating  copper  or  other 
ores  for  obtaining  their  contents  of  metals. — The  process  of  electrolyzing  a  solution 
of  a  metal;  to  deposit  the  metal  therefrom,  which  consists  in  passing  it  as  an  elec- 
trolyte through  a  succession  of  two  or  more  electrolytic  cells,  arranged  so  that 
the  cells  are  connected  in  electrical  series  with  a  source  of  electricity;  the  anodes 
insoluble,  the  electrodes  of  each  cell  in  electrical  multiple,  and  having  gradually 
increasing  surfaces,  whereby  there  is  a  gradual  reduction  of  the  current  density 
as  the  metal  of  the  electrolyte  is  deposited. 

704639 — July  15,  1902.  C.  HOEPFNER.  Leaching  and  extraction  of  metals 
from  their  ores. — The  process  of  extracting  metals,  which  consists  in  leaching  a 
suitable  material  containing  copper,  lead,  and  silver,  with  a  warm  cupric-chloride 
solution  containing  a  solvent  of  cuprous' chloride,  in  quantity  less  than  is  required 
for  saturation,  thereby  dissolving  lead  and  silver  chlorides,  precipitating  them, 
reconverting  the  solution  into  cupric  chloride,  using  the  same  for  leaching  fresh 
quantities  of  ore,  leaching  the  residues  with  a  similar  hot  solution  more  concen- 
trated in  cupric  chloride,  thereby  dissolving  copper  and  recovering  those  metals 
therefrom,  reconverting  the  resulting  solution  into  cupric  chloride,  and  returning 
the  latter  into  the  cycle  of  operations. 

706436 — August  5,  1902.  F.  T.  MUMFORD.  Apparatus  for  the  electrolytical 
treatment  of  ores  or  sfimes. — An  apparatus  for  the  extraction  of  metals  from  their 
ores  and  slimes,  comprising  a  rotatable  cylindrical  metallic  drum,  a  copper  lining 
therein,  a  body  of  mercury  in  the  drum  to  maintain  the  lining  amalgamated,  a 
valve-controlled  inlet  and  outlet,  and  a  relief- valve  at  one  end,  a  plurality  of  con- 
ductive rods  insulated  from  and  passing  longitudinally  through  the  drum,  a  metallic 
ring  connecting  the  bars,  trailing  electrical  contact  for  the  drum  and  one  for  said 
ring. 

709817 — September  23,  1902.  C.  E.  DOLBEAR.  Ehctrolytically  treating  ores. — 
The  method  of  reducing  metals  from  their  ores,  which  consists  in  dissolving  the 
crushed  ore  in  a  compound  containing  a  nitric  acid  radical,  adding  to  the  mix- 
ture sulphuric  acid,  and  subjecting  the  resultant  •  compound  to  the  action  of  an 
electric  current. 

725864 — April  21,  1903.  W.  B.  MCPHERSON.  Apparatus  for  the  treatment  of 
gold  or  other  ores. — A  precipitating  apparatus  for  d^po^iting  gold  and  silver  from 


PATENTS  RELATING  TO  CYANIDE  PROCESSES.      401 

a  cyanide  of  potassium  solution  and  from  other  chemical  solutions,  comprising 
a  precipitating-box  having  downward,  inclined  bottom  with  openings  therein, 
valves  located  in  said  openings,  said  box  provided  with  a  series  of  electric  con- 
ducting plates  vertically  arranged  therein  and  connected  with  a  source  of  electric 
supply,  a  gauge  receptacle,  a  pipe  communicating  with  said  receptacle  and  with 
the  precipitating-box  through  which  the  said  solution  passes  back  and  forth,  a 
float  within  said  receptacle  and  adapted  to  reciprocate  therein,  a  yoke  secured 
to  said  float,  a  horizontally  reciprocating  valve-rod,  devices  for  connecting  said 
yoke  with  said  valve-rod,  means  for  operating  said  valves  in  connection  with  valve- 
rod,  arid  means  for  conveying  said  solution  from  said  precipitating-box  and  return- 
ing the  same  thereto. 

737554 — August  25,  1903.  L.  P.  BURROWS.  Electrolytic  apparatus. — An 
electrolytic  apparatus,  comprising  a  dissolving  vessel  having  a  revoluble  anode, 
a  depositing  vessel  having  a  cathode,  means  for  conveying  an  unbroken  stream 
of  liquid  from  the  dissolving  vessel,  and  an  electric  circuit  including  said  anode 
and  cathode,  whereby  the  electric  current  is  caused  to  transverse  the  stream  of 
liquid  flowing  from  the  dissolving  vessel  into  the  depositing  vessel. 

741231— October  13,  1903.  W.  H.  DAVIS.  Process  of  treating  cyanide  solu- 
tions.— The  process  for  treating  cyanide  solutions  during  or  subsequently  to  their 
contact  with  the  ore,  consisting  in  introducing  into  the  solution  an  alkaline  hydrate 
and  then  subjecting  the  mixture  to  the  action  of  an  alternating  electric  current, 
thereby  raising  the  osmotic  pressure  to  dissociate  the  double  salts  in  the  solution, 
causing  precipitation  of  the  hydrates  of  the  base  metals  and  to  combine  the  freed 
cyanogen  with  the  alkaline  hydrates  to  cause  simultaneous  regeneration  of  the 
cyanide  in  the  solution  and  clarifying  of  the  latter. 

741439 — October  13,  1903.  C.  E.  BAKER  and  A.  W.  BURWELL.  Process  of 
treating  ores. — The  process  of  recovering  copper  and  nickel  from  a  solution  of  sul- 
phates of  copper,  nickel,  and  iron,  which  consists  of  electro-depositing  the  copper, 
neutralizing  the  solution,  and  electro-depositing  the  nickel  with  a  current  density 
insufficient  to  deposit  the  iron. 

743668 — November  10,  1903.  R.  SUCHY  and  H.  SPECKE'TER,  Extracting 
chromium  from  chrome-iron  ore. — The  process  of  making  soluble  chrome-iron  ore 
and  obtaining  chromium  compounds,  which  consists  in  heating  the  ore  together 
with  sulphuric  acid  in  excess  and  an  oxidizing  agent  and  separating  by  filtration 
the  precipitated  insoluble  ferrisulphate  from  the  chromosulpho  acid. 

749843 — January  19,  1904.  H.  R.  CASSEL.  Process  of  extracting  precious 
metals  by  electrolysis. — The  process  of  extracting  precious  metals  by  electrolysis, 
which  consists  in  circulating  the  pulp  between  vertical  electrodes,  amalgamating 
a  vertical  cathode,  successively  deflecting  the  rebounding  mercury  back  upon 
said  cathode,  removing  the  amalgam,  neutralizing  the  alkali  in  the  mercury,  and 
returning  the  mercury  to  the  cathode. 

749844 — January  19,  1904.  H.  R.  CASSEL.  Apparatus  for  extracting  precious 
metals  by  electrolysis. — An  apparatus  for  extracting  precious  metals  by  electrolysis, 
comprising  a  tank,  inclosed  vertical  electrodes,  mercury  deflectors,  and  pulp-guards 
at  the  sides  of  the  cathode,  an  elevated  pulp-box,  communicating  perforated  launders, 
means  for  lifting  the  pulp  into  said  box,  an  elevated  mercury  pot,  communicating 
slidable  perforated  troughs,  and  means  for  lifting  the  mercury  into  said  pot. 

755302 — March  22,  1904.  E.  A.  LE  SUEUR.  Extraction  of  copper  from  com- 
minuted mineral  mixtures, — The  method  of  obtaining  metallic  copper  from  mix- 
tures containing  it,  which  consists,  first  in  treating  said  mixtures  with  an  ammo- 
niacal  solution,  containing  a  cupric  compound  or  compounds,  so  as  to  dissolve 
the  desired  copper,  then  in  removing  a  portion  of  the  total  copper  contents  of 
the  solution,  and  lastly  in  using  the  partially  exhausted  solution  over  again  to 
dissolve  fresh  copper  as  before. 


INDEX. 


Acetonitrile,  40 

Adler's  process,  hydrocyanic  acid,  93 

Albright's  process,  sulphocyanide,  285 

Alcoholic  carbimides,  40 

Allyl  cyanide,  40 

Aluminium  cyanide,  24 

Ammonium  cyanate,  37 

cyanide,  23 
cyanhydrate,  60 
sulphocyanate,  274 

thiosulphocarbamate,  273 
Ammoniacal  liquors,  224 

cyanogen  from,  242 
Prussian  blue,  292 
Amyl  cyanide,  40 

Andreoli's  process,  gold  precipitation,  315 
Antimony  blue,  293 
Apparatus,  Bueb's,  186-8 

Castner's,  142,  174 

Engler's,  201 

Mackey's,  136 

Raschen's,  99 

Stassfurter  Chem.  Fabrik,  159 

Roca's,  167 

Arnpul,  Camille,  works  of,  248 
Auriferous  minerals,  oxidation  of,  295 
Auripotassic  cyanide,  35 
Aurocyanide,  35 
Aurosopotassic  cyanide,  35 
Azulmic  acid,  11 

Barium  cyanide,  24,  169 
ferricyanide,  32 

Beck's  process,  ferricyanide,  266 
Beilby's  process,  cyanide,  162 
Bergmann's  process,  hydrocyanic  acid,  94 

cyanide,  101 
results,  154 

Beringer's  process,  cyanide,  150 
Berthelot's  hypothesis,  7 
Black-mass,  composition  of,  204 
Blackmore's  process,  cyanides,  150 
Blood-lye,  81 
Blue  potash,  205 


Bouxvillers  Mines'  process,   ferricyanide, 

264 
Bower's  process,  cyanide,  107 

ferrocyanide,  243 

British  Cyanide  Co.'s  process,  cyanide,  105 

sulphocya- 
nide, 283 

Brock's  process,  sulphocyanide,  282 
Brunquell's  process,  cyanide,  153 

ferrocyanide,  210 
Bueb's  apparatus,  186 

process,  cyanide,  185 

ferrocyanide,  237 

Buignet's  method,  hydrocyanic  acid,  48 
Burchell's  method,  52 
Butyl  cyanate,  40 
cyanide,  40 
Butyro  nitrile,  40 

Calcium  cyanide,  24 

ferricyanide,  32 

sulphocyanate,    preparation    of, , 

277 

Carbazol,  183 
Carbylamines,  39 
Castner's  process,  cyanide,  153 
Cetyl  cyanide,  40 
Chaster' s  process,  cyanide,  165 

hydrocyanic  acid,  88 
Chem.  Fabrik  Aktiengesellschaft's  process, 

cyanide,  165 

Chlorides,  detection  of,  47 
Chlorine  process,  ferricyanides,  261 
Chromium  cyanide,  25 
Chryseane,  21 
Clark's  process,  16 

Clauss   and   Domeier's   process,  ferrocya- 
nide, 234 
Coal,  nitrogen  content  of,  220 

types  of,  216 
Cobalt  cyanide,  27 

ferricyanide,  32 

Cobalticyanide  of  potassium,  34 
sodium,  34 

403" 


404 


INDEX. 


Cobaltocobalticyanide,  34 

Coke,  elements  of,  218 

Compagnie  Generate  des  Cyanures,  273 

Conroy's  process,  cyanide,  108 

ferrocyanide,  211 
Cooling-mixture,  329 
Copper  cyanide,  26 

ferricyanide,  32 
Crystallization,  210 
Cyanamid,  147 
Cyanate  of  ammonium,  37 
silver,  37 
sodium,  37 
Cyanates,  44 

detection  of,  47 
Hertig's  method,  47 
Cyanic  acid,  36 

esters,  40 

Cyanide  of  aluminium,  24 
ammonium,  23 
barium,  24 
calcium,  24 
cobalt,  27 
copper,  26 
chromium,  25 
gold,  27 
iron,  25 
manganese,  25 
mercury,  26 
nickel,  27 
platinum,  27 
silver,  26 
sodium,  23 
tin,  25 
zinc,  24 

'Cyanides,  analysis  of  commercial,  47 
characteristics  of,  328 
critical  temperatures,  324 
density  of,  323,  329 
determination     of      medicinal, 

48 

double,  28 
extraction     from     illuminating 

gas,  214,  219 

extraction   from  purifying  ma- 
terials, 245 
extraction      from      sulphocya- 

nides,  95 

Fordos  and  Gelis'  method,  45 
iieat  of  formation,  56,  324 
solution,  324 
volatilization,  324 
O.  Hertig's  method,  47 
Liebig's  method,  44 
list  of  works  producing,  74 
methods  of  manufacture,  81 
simple,  22 
solubility  of,  327 
strong  solution,  301 
use  of,  294 
weak  solutions,  302 


Cyanides — manufacturing  processes* 

Adler's  process,  93 

Armengaud's  process,  126 

Beilby's  process,  162 

Bergmann's  process,  94 

Beringer's  process,  101,  150 

Blackmore's  process,  150 

Blairs'  process,  126 

Boussingault's  process,  119 

Bower's  process,  107 

British  Cyanide  Co.'s  process,  105 

Brunquell's  process,  153 

Bueb's  process,  185 

Bunsen's  process,  123 

Castner's  process,  141,  153,  172 

Chaster's  process,  88,  165 

Chem.  Fabrik  Aktiengesellschaft's, 
183 

Chem.  Fabrik  Pfersee  Augsburg,  149 

Chipmann's  process,  138 

Conroy's  process,  107 

Dalinot's  process,  92 

Deutsche  Gold  u.  Silber  Scheide 
Anstalt,  175 

Dickson's  process,  129 

Dzuik's  process,  150 

Etard's  process,  110,  120 

Finlay's  process,  110 

Fogarty's  process,  128 

Frank  and  Caro's  process,  144,  153 

Gen.  Elec.  Chem.  Co.'s  process,  152 

Gilmour's  process,  134 

Glock's  process,  179 

Goerlich  and  Wichmann's  process,  107 

Grossmann's  process,  182 

Hetherington  and  Musspratt's  proc- 
ess, 106 

Hood  and  Salamon's  process,  169 

Hornig's  process,  170 

Hornig  and  Schneider's  process,  143 

Hoyermann's  process,  180 

Huntington's  process,  180 

Karmrodt's  process,  153 

Kellner's  process,  182 

Kerp's  process,  181 

Lambilly's  process,  129,  161,  178 

Lance  and  Bourgade's  process,  156 

Liebig's  process,  87,  153 

Lucas'  process,  153 

Luttke's  process,  104 

Mackey's  process,  135 

Mactear's  process,  157 

Mallet's  process,  121 

Margueritte  and  SourdevaFs  process, 
126,  153 

Martin's  process,  179 

Mehner's  process,  137,  143 

Moi'se  and  Mehner's  process,  140 

Mond's  process,  127 

Moulis  and  Sars'  process,  160 

Newton's  process,  126 


INDEX. 


405 


Cyanides — manufacturing  processes : 
Old  processes,  85 
Ortlieb  and  Miiller's  process,  190 
Parkinson's  process,  120 
Pestchow's  process,  137 
Pictet's  process,  121 
Pfleger's  process,  165 
Playf air's  process,  102 
Possoz  and  Boissiere' s  process,  124 
Raschen  and  Brock's  process,  97,  110 
Readmann's  process,  135 
Roca's  process,  166 
Rossler  and  Haaslacher's  process,  89 
Roussin's  process,  181 
Schneider's  process,  171 
Silesia  Verein  Chem.  Fabrik's  process, 

107 
Societe  Anonyme  de  Croix's  process, 

190 
Stassfurter  Chem.  Fabrick's  process, 

158 

Swan  and  Kendall's  process,  137 
Synthetic  processes,  111 
Tessie'  du  Mothay's  process,  120 
Vidal's  process,  184 
Villepigne's  process,  121 
Wagner's  process,  88 
Weldon's  process,  128 
Wichmann  and  Vautin's  process,  88 
Wolfram's  process,  150 
Young's  process,  134 
Young  and  Macfarlane's  process,  163 
Cyaniding  mixture,  168 
Cyanogen,  constitution  of ,5 

conversion  tension,  14 

formation,  12 

preparation,  13 

properties,  10 
Cyanosulphite  of  potassium,  22 

Dalinot's  process,  hydrocyanic  acid,  92 

Deiss  and  Monnier's  process,  sulphocya- 
nide,  281 

Deutsche  Gold  u.  Silber  Scheide  Anstalt's 
process,  ferrocyanide,  265 

DeWilde's  process,  303 

Donath's  process,  ferrocyanide,  258 

Donath  and  Margosche's  method,  ferrocya- 
nide, 53 

Double  cyanides,  28 

Dubosc's  process,  ferricyanide,  265 

du  Castelet  Works'  process,  ferrocyanide, 
213 

Dzuik's  process,  cyanide,  150 

En^ler's  apparatus,  201 
Erlenmeyer's  method,  ferrocyanide,  49 
Esop's  process,  ferrocyanide,  258 
Etard's  process,  hydrocyanic  acid,  94 
Ethyl  cyanate,  40 
cyanide,  40 


Everitt's  process,  16 
Feld's  process,  ferrocyanide,  241 
Ferricyanide,  manufacture  of,  261 
of  potassium,  43,  32 
Ferricyanide  processes : 

Beck's  process,  267 

Chlorine  process,  261 

Deutsche  Gold  u.  Silber  Scheide  An- 
stalt's process,  265 

Dubosc's  process,  265 

Kassner's  process,  266 

Mines  at  Bouxvillers,  264 

Reichardt's  process,  263 

Williamson's  process,  267 
Ferricyanide,  use  of,  319 
Ferrocyanide,  25,  43 

manufacture  of,  192,  205, 

229 
Ferrocyanide  processes : 

Bower's  process,  243 

BrunquelPs  process,  210 

Bueb's  process,  237 

Glaus  s  and  Domeier's  process,  234 

Conroy's  process,  212 

Donath's  process,  258 

Esop's  process,  258 

Feld's  process,  241 

Fowlis'  process,  233 

Gasch's  process,  232 

Gauthier-Bouchard's  process,  248 

Goerlich  and  Wichmann' s  process,  213 

Harcourt's  process,  257 

Hempel's  process,  257 

Hetherington's  process,  212 

Holbling's  process,  259 

Karmrodt's  process,  211 

Knublauch's  process,  231 

Kunheim's  process,  257 

Lewis'  process,  236,  243,  259 

Marasse's  process,  258 

Mascow's  process,  259 

Musspratt's  process,  212 

Pendrie's  process,  242 

Richter's  process,  258 

Rowland's  process,  233 

Schroeder's  process,  234 

Teichmann's  process,  235 

Valentin's  process,  256 

Wolfram's  process,  257 

Works  du  Castelet,  213 
Ferrocyanide,  detection  of: 

Burchell's  method,  52 

Erlenmeyer's  method,  49 

Knublauch's  method,  50 

Moldenhauer  and  Leybold's  method, 

51 
Ferrocyanide  of  iron,  31 

potassium,  29 
sodium,  31 

Ferrocyanide,  precipitation  of,  253 
use  of,  316 


406 


INDEX. 


Filtering-vats,  300 

Flemming's  furnace,  158 

Fordos  and  Gelis'  method,  45 

Formates,  detection  of,  47 

Frank  and  Caro's  process,  cyanide,  144 

Furnaces,  Flemming's,  158 
Gruneberg's,  158 
reverberatory,  199 
Siepermann's,  158,  182 

Gas,  composition  of,  226 

Gasch's  process,  ferrocyanide,  232 

Gauthier-Bouchard's     process,    ferrocya- 
nide, 248 

Gelis'  process,  sulphocyanide,  272 

Gen.  Elec.-Chem.  Co.'s  process,  cyanide, 
182 

Goerlich  and  Wichmann's  process,  cyanide, 
107 

Goerlich  and  Wichmann's  process,  ferrocy- 
anide, 213 

Goerlich  and  Wichmann's  process,  sulpho- 
cyanide, 286 

Gold-bromine  cyanide,  formation,  297 

Gold  cyanide,  35 

precipitation  of,  298,  304,  314 
solution  of,  298 

Grossmann's  process,  cyanide,  182 

Gruneberg's  furnace,  158 

Harcourt's  process,  ferrocyanide,  257 
HempePs  process,  ferrocyanide,  257 
Hertig's  method,  cyanates,  47 
Hetherington's  process,  ferrocyanide,  212 
Hetherington    and    Musspratt's    process, 

cyanide,  106 

Holbling's  process,  ferrocyanide,  259 
Hood  and  Salamon's  process,  cyanide,  169 

sulphocya- 
nide, 282 

Hornig's  process,  cyanide,  170 
Hornig  and  Schneider's  process,  cyanide, 

143 

Hydrate  of  iron,  composition,  247 
Hydrocyanic  acid,  14,  42 

Buignet's  method,  48 
heat  of  formation,  57 
Hydrocyanic  acid: 

Adler's  process,  93 

Bergmann's  process,  94 

Chaster's  process,  88 

Dalinot's  process,  92 

Etard's  process,  94 

Liebig's  process,  87 

Rossler  and  Haaslacher's  process,  89 

Wagner's  process,  88 

Wichmann's  and  Vautin's  process,  90 

Illuminating-gas,  composition,  226 
elements  of,  218 


Karmrodt's  process,  cyanide,  153 

ferrocyanide,  211 
Kassner's  process,  ferricyanide,  266 
Keith's  process,  gold  precipitation,  314 
Kellner's  process,  cyanide,  182 
Kerp's  process,  cyanide,  181 
Knublauch's  process,  ferrocyanide,  231 
Kunheim's  process  ferrocyanide,  257 

Lambilly's  process,  cyanide,  153,  161 
Laming  mixture,  composition,  246 
Lance  and  Bourgade's  process,cyanide,156 
Lewis'  process,  ferrocyanide,  236,  243,  259 
Liebig's  method,  cyanide,  44 

process,  cyanide,  153 

hydrocyanic  acid,  87 

theory,  9 

Limonite,  composition  of,  247 
Lixiviation,  210,  249 
vats,  252 

Lucas'  process,  cyanide,  153 
Luttke's  process,  cyanide,  104 
Lux  mass,  composition,  246 

MacArthur  and  Forrest's  method,  3041 
Mackey's  process,  cyanide,  135 
Mactear's  process,  cyanide,  157 
Manganese  cyanides,  25,  34 
Marasse's  process,  ferrocyanide,  258 
Margueritte's  process,  cyanide,  153 
Margueritte  and  SourdevaFs  process,  cya- 
nide, 126 

Martin's  process,  cyanide,  179 
Mascow's  process,  ferrocyanide,  258 
Mehner's  process,  cyanide,  143 
Melam,  39 
Mercury  cyanide,  26 
Metal,  production  of,  197 
Metallic  cyanides,  18 
Methyl  cyanate,  46 
cyanide,  40 

Moise  and  Mehner's  process,  cyanides,  140* 
Moldenhauer  and  Leybold's  method,  51 
Mond's  process,  cyanide,  127 
Monthier's  blue,  292 
Moulis  and  Sars'  process,  cyanide,  160 
Mulholland's  process,  303 
Musspratt's  process,  ferrocyanide,  212 

Newton's  process,  cyanide,  126 
Nickel  cyanide,  27 

ferricyanide,  32 
Nitriles,  39 
Nitroferricyanides,  35 
Nitroprussiates,  35 
Non-synthetic  processes,  85 

Old  process,  cyanide,  85 

ferrocyanide,  193 
Organic  compounds,  39 
Ortlieb  &  Miiller's  process,  cyanide,  190' 


INDEX. 


407 


Oxide  of  iron,  composition  of,  247 
Oxygen  compounds  of  cyanogen,  36 

Paracyanogen,  13,  147 
Pendrie's  process,  ferrocyanide,  242 
Pfleger's  process,  cyanide,  165 
Physical  study  cyanogen,  10 
Platinum  cyanide,  27 
Platino  cyanides,  34 
Playfair's  process,  cyanide,  102 
Potash,  determination  of,  48 
Potassium  cyanate,  36,  60 
cyanide,  20,  58 

analysis  of,  47 
antidote,  22 
heat  of  formation,  58 
manufacture,  85 
production,  72 
use  of,  70 
cyaniferride,  32 
cyanosulphite,  21 
ferricyanide,  32 

production,  72 
ferrocyanide,  29,  43,  49 

exportation,  80 
heat    of     forma- 
tion, 60 

importation,  79 
production,  72 
sulphide,  detection,  47 
sulphocyanide,  38 
Processes  utilizing  ammonia,  153 

atmospheric  nitrogen, 

117 

Propionitrile,  40 
Propyl  cyanide,  40 
Prussian  blue,  31 

determination,  54 
discovery  of,  69 
manufacture,  288 
use  of,  319 

Woodward's  method,  289 
Prussic  acid,  14 

action  on  system,  17 
antidote,  18 
Purifying  materials,  50 

composition,  of,  219, 

226,  245 
revivification,  247 

Raschen' s  apparatus,  99 
Raschen  and  Brock's  method,  97 
Raschen,  Davidson  and  Brock's  process, 

cyanide,  110 

Readmann's  process,  cyanide,  135 
Red  prussiate  of  potash,  32 
Reichardt's  process,  ferricyanides,  263 
Retort,  198 
Rhodanides,  37 

Richter's  process,  ferrocyanides,  258 
Roca's  apparatus,  167 


process,  cya- 


Roca's  process,  cyanide,  166 
Rossler  and  Haaslacher's  process,  hydro- 
cyanic acid,  89 

Roussin's  process,  cyanides,  181 
Rowland's  process,  ferrocyanide,  233 

Schneider's  process,  cyanide,  171 
Schroeder's  process,  ferrocyanide,  234 
Siemens  and  Halske's   process,  gold  pre- 
cipitation, 314 

Siepermann's  furnace,  158,  182 
Silesia  Verein  Chem.  Fabrik's  pr 

nide,  107 
Silver  cyanate,  37 
cyanide,  26 
ferricyanide,  32 
Simple  cyanide,  formation,  19 
properties,  19 

Socie'te'  Anonyme  de  Croix's  process,  cya- 
nide, 190 

Sodium  cyanate,  37 
cyanide,  23 
ferrocyanide,  31 
Soluble  Prussian  blue,  32,  292 
Sourdeval's  process,  cyanide,  153 
Spent  oxide,  54 

composition,  246 

Stassfurter  Chem.  Fabrik's  process,  cya- 
nide, 158 

Sulman's  process,  303 
Sulphate  of  iron,  composition  of,  247 
Sulphocarbamide,  39 
Sulphocyanates,  37 
Sulphocyanide,  37,  43,  50 
cost  of,  271 
detection  of,  47 
manufacture,  269 
Sulphocyanide  processes : 
Albright's  process,  285 
British  Cyanide  Co.'s  process,  283' 
Brock's  process,  282 
Deiss  and  Monnier's  process,  281 
Gelis'  process,  270 

Goerlich  and  Wichmann's  process,  286'- 
Hood  and  Salamon's  process,  282 
Tcherniac's  process,  285 
Sulphocyanide  recovery,  56 

use  of,  319 

Swan  and  Kendall's  process,  cyanide,  137 
Synthetic  processes,  cyanide,  111 

Tables,  294 

Tar,  218 

Tcherniac's  process,  sulphocyanide,  285  . . 

Teichmann's  process,  ferrocyanide,  235  , 

Tin  cyanide,  25 

Thomson's  process,  16 

Toxicological  research,  54 

Tricyanates,  37  i 

TurnbulPs  blue,  33,  292 

Valentin's  process,  ferrocyanide,  256:         *• 


408 


INDEX. 


Vats,  filtering,  299 
Vauquelin's  process,  16 
Vidal's  process,  cyanide,  184 

Wagner's  process,  cyanide,  88 
Weldon's  process,  cyanide,  127 
Wichmann  and  Vautin's  process,  cyanide, 

90 

Williamson's  process,  ferricyanide,  267 
Wolfram's  process,  cyanide,  150 


Wolfram's  process,  ferrocyanide,  257 
Woodward's  method,  289 

Young's  process,  cyanide,  134 
Young  and  Macfarlane's  process,  cyanide, 
163 

Zaloziecki's  method,  ferrocyanide,  52 
Zinc  cyanide,  24 

potassium  cyanide,  22 


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Skeleton  Construction  in  Buildings 8vo,  3  oo 

Brigg's  Modern  American  School  Buildings 8vo,  4  oo 

Carpenter's  Heating  and  Ventilating  of  Buildings 8vo,  4  oo 

Freitag's  Architectural  Engineering 8vo,  3  50 

Fireproofing  of  Steel  Buildings 8vo,  2  50 

French  and  Ives's  Stereotomy 8vo,  2  50 

1 


Gerhard's  Guide  to  Sanitary  House-inspection i6mo,  i  oo 

Theatre  Fires  and  Panics i2mo,  i  50 

•Greene's  Structural  Mechanics 8vo,  2  50 

Holly's  Carpenters'  and  Joiners'  Handbook i8mo,  75 

Johnson's  Statics  by  Algebraic  and  Graphic  Methods 8vo,  2  oo 

Kidder's  Architects'  and  Builders'  Pocket-book.  Rewritten  Edition.  i6mo,  mor.,  5  oo 

Merrill's  Stones  for  Building  and  Decoration , . . .  .8vo,  5  oo 

Non-metallic  Minerals:   Their  Occurrence  and  Uses 8vo,  4  oo 

Monckton's  Stair-building 4to,  4  oo 

Patton's  Practical  Treatise  on  Foundations 8vo,  5  oo 

Peabody's  Naval  Architecture 8vo,  7  50 

Richey's  Handbook  for  Superintendents  of  Construction i6mo,  mor.,  4  oo 

Sabin's  Industrial  and  Artistic  Technology  of  Paints  and  Varnish 8vo,  3  oo 

Siebert  and  Biggin's  Modern  Stone-cutting  and  Masonry 8vo,  i  50 

Snow's  Principal  Species  of  Wood 8vo,  3  50 

Sondericker's  Graphic  Statics  with  Applications  to  Trusses,  Beams,  and  Arches. 

8vo,  2  oo 

Towne's  Locks  and  Builders'  Hardware i8mo,  morocco,  3  oo 

Wait's  Engineering  and  Architectural  Jurisprudence 8vo,  6  oo 

Sheep,  6  50 

Law  of  Operations  Preliminary  to  Construction  in  Engineering  and  Archi- 
tecture  8vo,  5  oo 

Sheep,  5  50 

Law  of  Contracts. 8vo,  3  oo 

Wood's  Rustless  Coatings :  Corrosion  and  Electrolysis  of  Iron  and  Steel .  .  8vo,  4  oo 
Worcester  and  Atkinson's  Small  Hospitals,  Establishment  and  Maintenance, 
Suggestions  for  Hospital  Architecture,  with  Plans  for  a  Small  Hospital. 

i2mo,  i  25 

The  World's  Columbian  Exposition  of  1893 Large  4to,  i  oo 


ARMY  AND  NAVY. 

Bernadou's  Smokeless  Powder,  Nitro-cellulose,  and  the  Theory  of  the  Cellulose 

Molecule i2mo,  2  50 

*  Bruff 's  Text-book  Ordnance  and  Gunnery 8vo,  6  oo 

Chase's  Screw  Propellers  and  Marine  Propulsion 8vo,  3  oo 

Cloke's  Gunner's  Examiner 8vo,  i  50 

Craig's  Azimuth 4to,  3  50 

Crehore  and  Squier's  Polarizing  Photo-chronograph 8vo,  3  oo 

*  Davis's  Elements  of  Law 8vo,  2  50 

*  Treatise  on  the  Military  Law  of  United  States 8vo,  7  oo 

Sheep,  7  50 

De  Brack's  Cavalry  Outposts  Duties.     (Carr.) 24010,  morocco,  2  oo 

Dietz's  Soldier's  First  Aid  Handbook i6mo,  morocco,  i  25 

*  Dredge's  Modern  French  Artillery 4to,  half  morocco,  15  oo 

Durand's  Resistance  and  Propulsion  of  Ships 8vo,  5  oo 

*  Dyer's  Handbook  of  Light  Artillery I2mo,  3  oo 

Eissler's  Modern  High  Explosives 8vo,  4  oo 

*  Fiebeger's  Text-book  on  Field  Fortification Small  8vo,  2  oo 

Hamilton's  The  Gunner's  Catechism i8mo,  i  oo 

*  Hoff's  Elementary  Naval  Tactics 8vo,  i  50 

Ingalls's  Handbook  of  Problems  in  Direct  Fire 8vo,  4  oo 

*  Ballistic  Tables 8vo,  i  50 

*  Lyons's  Treatise  on  Electromagnetic  Phenomena.  Vols.  I.  and  II.  .8vo,  each,  6  oo 

*  Mahan's  Permanent  Fortifications.    (Mercur.) 8vo,  half  morocco,  7  50 

Manual  for  Courts-martial i6mo,  morocco,  i  50 

*  Mercur's  Attack  of  Fortified  Places i2mo,  2  oo 

*  Elements  of  the  Art  of  War 8vo,  4  oo 

2 


Metcalf's  Cost  of  Manufactures — And  the  Administration  of  Workshops.  .8vo,  5  oo 

*  Ordnance  and  Gunnery.     2  vols I2mo,  5  oo 

Murray's  Infantry  Drill  Regulations i8mo,  paper,  10 

Nixon's  Adjutants'  Manual 24010,  I  oo 

Peabody's  Naval  Architecture 8vo,  7  50 

*  Phelps's  Practical  Marine  Surveying. 8vo,  2  50 

Powell's  Army  Officer's  Examiner i2mo,  4  oo 

Sharpe's  Art  of  Subsisting  Armies  in  War i8mo,  morocco,  50 

*  Walke's  Lectures  on  Explosives 8vo,  oo 

*  \  fheeler's  Siege  Operations  and  Military  Mining 8vo,  oo 

Winthrop's  Abridgment  of  Military  Law i2mo,  50 

Wcodhull's  Notes  on  Military  Hygiene i6mo,  50 

Young's  Simple  Elements  of  Navigation z6mo,  morocco-  oo 


ASSAYING. 

Fletcher's  Practical  Instructions  in  Quantitative  Assaying  with  the  Blowpipe. 

i2mo,  morocco,  i  50 

Furman's  Manual  of  Practical  Assaying 8vo,  3  oo 

Lodge's  Notes  on  Assaying  and  Metallurgical  Laboratory  Experiments.  .  .  .8vo,  3  oo 

Low's  Technical  Methods  of  Ore  Analysis 8vo,  3  oo 

Miller's  Manual  of  Assaying i2mo,  i  oo 

Minet's  Production  of  Aluminum  and  its  Industrial  Use.     (Waldo.) i2mo,  2  50 

O'Driscoll's  Notes  on  the  Treatment  of  Gold  Ores 8vo,  2  oo 

Ricketts  and  Miller's  Notes  on  Assaying 8vo,  3  oo 

Robine  and  Lenglen's  Cyanide  Industry.     (Le  Clerc.) 8vo, 

Ulke's  Modern  Electrolytic  Copper  Refining 8vo,  3  oo 

Wilson's  Cyanide  Processes i2mo,  i  50 

Chlorination  Process i2mo,  i  50 


ASTRONOMY. 

Comstock's  Field  Astronomy  for  Engineers 8vo,  2  50 

Craig's  Azimuth 4to,  3  30 

Doolittle's  Treatise  on  Practical  Astronomy 8vo,  4  oo 

Gore's  Elements  of  Geodesy 8vo,  2  50 

Hayford's  Text-book  of  Geodetic  Astronomy , 8vo,  3  oo 

Merriman's  Elements  of  Precise  Surveying  and  Geodesy. 8vo,  2  50 

*  Michie  and  Harlow's  Practical  Astronomy 8vo,  3  oo 

*  White's  Elements  of  Theoretical  and  Descriptive  Astronomy i2mo,  2  oo 


BOTANY. 

Davenport's  Statistical  Methods,  with  Special  Reference  to  Biological  Variation. 

i6mo,  morocco,  i  25 

Thomd  and  Bennett's  Structural  and  Physiological  Botany i6mo,  2  25 

Westermaier's  Compendium  of  General  Botany.     (Schneider.) 8vo,  2  oo 


CHEMISTRY. 

Adriance's  Laboratory  Calculations  and  Specific  Gravity  Tables i2mo,  i  25 

Allen's  Tables  for  Iron  Analysis 8vo,  3  oo 

Arnold's  Compendium  of  Chemistry.     (Mandel.) Small  8vo,  3  50 

Austen's  Notes  for  Chemical  Students i2mo,  i  50 

Bernadou's  Smokeless  Powder. — Nitro-cellulose,  and  Theory  of  the  Cellulose 

Molecule I2mo,  2  50 

*  Browning's  Introduction  to  the  Rarer  Elements 8vo,  i  50 

3 


Brush  and  Penfield's  Manual  of  Determinative  Mineralogy 8vo,  4  oo 

Classen's  Quantitative  Chemical  Analysis  by  Electrolysis.    (Boltwood.).  -8vo,  3  oo 

Cohn's  Indicators  and  Test-papers lamo,  2  oo 

Tests  and  Reagents 8vo,  3  oo 

Crafts's  Short  Course  in  Qualitative  Chemical  Analysis.   (Schaeffer.).  .  .i2mo,  i  50 
Dolezalek's  Theory  of  the   Lead  Accumulator   (Storage   Battery).        (Von 

Ende.) i2mo,  2  50 

Drechsel's  Chemical  Reactions.     (Merrill.) i2mo,  i  25 

Duhem's  Thermodynamics  and  Chemistry.     (Burgess.) 8vo,  4  oo 

Eissler's  Modern  High  Explosives 8vo,  4  oo 

Eff rent's  Enzymes  and  their  Applications.     (Prescott.) 8vo,  3  oo 

Erdmann's  Introduction  to  Chemical  Preparations.     (Dunlap.) i2mo,  i  25 

Fletcher's  Practical  Instructions  in  Quantitative  Assaying  with  the  Blowpipe. 

i2mo,  morocco,  i  50 

Fowler's  Sewage  Works  Analyses i2mo,  2  oo 

Fresenius's  Manual  of  Qualitative  Chemical  Analysis.     (Wells.) 8vo,  5  oo 

Manual  of  Qualitative 'Chemical  Analysis.  Part  I.  Descriptive.  (Wells.)  8vo,  3  oo 
System  of    Instruction    in    Quantitative    Chemical   Analysis.      (Cohn.) 

2  vols 8vo,  12  50 

Fuertes's  Water  and  Public  Health 12010,  i  50 

Furman's  Manual  of  Practical  Assaying .8vo,  3  oo 

*  Getman's  Exercises  in  Physical  Chemistry i2mo,  2  oo 

Gill's  Gas  and  Fuel  Analysis  for  Engineers 1 12mo,  i  25 

Grotenfelt's  Principles  of  Modern  Dairy  Practice.     (Woll.) 12010,  2  oo 

Hammarsten's  Text-book  of  Physiological  Chemistry.     (Mandel.) 8vo,  4  oo 

Helm's  Principles  of  Mathematical  Chemistry.     (Morgan.) i2mo,  i  50 

Bering's  Ready  Reference  Tables  (Conversion  Factors) i6mo,  morocco,  2  50 

Hind's  Inorganic  Chemistry 8vo,  3  oo 

*  Laboratory  Manual  for  Students i2mo,  i  oo 

Holleman's  Text-book  of  Inorganic  Chemistry.     (Cooper.) 8vo,  2  50 

Text-book  of  Organic  Chemistry.     (Walker  and  Mott.) 8vo,  2  50 

*  Laboratory  Manual  of  Organic  Chemistry.     (Walker.) i2mo,  i  oo 

Hopkins's  Oil-chemists'  Handbook 8vo,  3  oo 

Jackson's  Directions  for  Laboratory  Work  in  Physiological  Chemistry.  .8vo,  i  25 

Keep's  Cast  Iron 8vo,  2  so 

Ladd's  Manual  of  Quantitative  Chemical  Analysis i2mo,  i  oo 

Landauer's  Spectrum  Analysis.     (Tingle.) 8vo,  3  oo 

*  Langworthy  and  Austen.        The  Occurrence  of  Aluminium  in  Vegetable 

Products,  Animal  Products,  and  Natural  Waters 8vo,  2  oo 

Lassar-Cohn's  Practical  Urinary  Analysis.  (Lorenz.) i2mo,  i  oo 

Application  of  Some  General  Reactions  to  Investigations  in  Organic 

Chemistry.  (Tingle.) 12010,  i  oo 

Leach's  The  Inspection  and  Analysis  of  Food  with  Special  Reference  to  State 

Control 8vo,  7  50 

Lob's  Electrochemistry  of  Organic  Compounds.  (Lorenz.) 8vo,  3  oo 

Lodge's  Notes  on  Assaying  and  Metallurgical  Laboratory  Experiments 8vo,  3  oo 

Low's  Technical  Method  of  Ore  Analysis 8vo,  3  oo 

Lunge's  Techno-chemical  Analysis.  (Cohn.) 12010,  i  oo 

Mandel's  Handbook  for  Bio-chemical  Laboratory 12010,  i  50 

*  Martin's  Laboratory  Guide  to  Qualitative  Analysis  with  the  Blowpipe .  .  12010,  60 
Mason's  Water-supply.     (Considered  Principally  from  a  Sanitary  Standpoint.) 

3d  Edition,  Rewritten 8vo,  4  oo 

Examination  of  Water.     (Chemical  and  Bacteriological.) 12010,  i  25 

Matthew's  The  Textile  Fibres 8vo,  3  So 

Meyer's  Determination  of  Radicles  in  Carbon  Compounds.     (Tingle.).  .i2mo,  i  oo 

Miller's  Manual  of  Assaying 12010,  i  oo 

Minet's  Production  of  Alumioum  and  its  Industrial  Use.     (Waldo.) .  .  .  .  i2mo,  2  50 

Mixter's  Elementary  Text-book  of  Chemistry 12010,  i  50 

Morgan's  Elements  of  Physical  Chemistry 12010,  3  oo 

*  Physical  Chemistry  for  Electrical  Engineers i2mo,  i  50 

4 


Morse's  Calculations  used  in  Cane-sugar  Factories i6mo,  morocco,  i  50 

Mulliken's  General  Method  for  the  Identification  of  Pure  Organic  Compounds. 

Vol.  I Large  8vo,  5  oo 

O'Brine's  Laboratory  Guide  in  Chemical  Analysis 8vo,  2  oo 

O'DriscolTs  Notes  on  the  Treatment  of  Gold  Ores 8vo,  2  oo 

Ostwald's  Conversations  on  Chemistry.     Part  One.     (Ramsey.) 12:010,  i  50 

"                   "               "           "             Part  Two.     (Turnbull.) I2mo,  2  oo 

*  Penfield's  Notes  on  Determinative  Mineralogy  and  Record  of  Mineral  Tests. 

8vo,  paper,  50 

Pictet's  The  Alkaloids  and  their  Chemical  Constitution.     (Biddle.) 8vo,  5  oo 

Pinner's  Introduction  to  Organic  Chemistry.     (Austen.) i2mo,  i  50 

Poole's  Calorific  Power  of  Fuels 8vo,  3  oo 

Prescott  and  Winslow's  Elements  of  Water  Bacteriology,  with  Special  Refer- 
ence to  Sanitary  Water  Analysis i2mo,  i  25 

*  Reisig's  Guide  to  Piece-dyeing 8vo,  25  oo 

Richards  and  Woodman's  Air,  Water,  and    Food  from  a  Sanitary  Stand- 
point  8vo,  .  2  oo 

Richards's  Cost  of  Living  as  Modified  by  Sanitary  Science i2mo,  i  oo 

Cost  of  Food,  a  Study  in  Dietaries I2mo,  i  oo 

*  Richards  and  Williams's  The  Dietary  Computer 8vo,  i  50 

Ricketts  and  Russell's  Skeleton  Notes  upon  Inorganic  Chemistry.     (Part  I. 

Non-metallic  Elements.) 8vo,  morocco,  75 

Ricketts  and  Miller's  Notes  on  Assaying .8vo,  3  oo 

Rideal's  Sewage  and  the  Bacterial  Purification  of  Sewage 8vo,  3  50 

Disinfection  and  the  Preservation  of  Food 8vo,  4  oo 

Rigg's  Elementary  Manual  for  the  Chemical  Laboratory 8vo,  i  25 

Robine  and  Lenglen's  Cyanide  Industry.     (Le  Clerc.) 8vo, 

Rostoski's  Serum  Diagnosis.     (Bolduan.) I2mo,  i  oo 

Ruddiman's  Incompatibilities  in  Prescriptions 8vo,  2  oo 

*  Whys  in  Pharmacy I2mo,  i  oo 

Sabin's  Industrial  and  Artistic  Technology  of  Paints  and  Varnish 8vo,  3  oo 

Salkowski's  Physiological  and  Pathological  Chemistry.     (Orndorff.) 8vo,  2  50 

Schimpf's  Text-book  of  Volumetric  Analysis I2mo,  2  50 

Essentials  of  Volumetric  Analysis.  .  ." I2mo,  i  25 

*  Qualitative  Chemical  Analysis 8vo,  i  25 

Spencer's  Handbook  for  Chemists  of  Beet-sugar  Houses i6mo,  morocco,  3  oo 

Handbook  for  Cane  Sugar  Manufacturers i6mo,  morocco,  3  oo 

Stockbridge's  Rocks  and  Soils 8vo,  2  50 

*  Tillman's  Elementary  Lessons  in  Heat 8vo,  i  50 

*  Descriptive  General  Chemistry 8vo,  3  oo 

Treadwell's  Qualitative  Analysis.     (Hall.) 8vo,  3  oo 

Quantitative  Analysis.     (Hall.) 8vo,  4  oo 

Turneaure  and  Russell's  Public  Water-supplies 8vo,  5  oo 

Van  Deventer's  Physical  Chemistry  for  Beginners.     (Boltwood.) i2mo,  i  50 

*  Walke's  Lectures  on  Explosives 8vo,  4  oo 

Ware's  Beet-sugar  Manufacture  and  Refining Small  8vo,  cloth,  4  oo 

Washington's  Manual  of  the  Chemical  Analysis  of  Rocks 8vo,  2  oo 

Wassermann's  Immune  Sera :  Haemolysins,  Cytotoxins,  and  Precipitins.    (Bol- 
duan.)  i2mo,  i  oo 

Well's  Laboratory  Guide  in  Qualitative  Chemical  Analysis 8vo,  i  50 

Short  Course  in  Inorganic  Qualitative  Chemical  Analysis  for  Engineering 

Students I2mo,  i  50 

Text-book  of  Chemical  Arithmetic I2mo,  i  25 

Whipple's  Microscopy  of  Drinking-water 8vo,  3  50 

Wilson's  Cyanide  Processes lamo,  i  50 

Chlorination  Process I2mo,  I  50 

Winton's  Microscopy  of  Vegetable  Foods 8vo,  7  50 

Wulling's    Elementary*  Course    in  Inorganic,  Pharmaceutical,  and  Medical 

Chemistry I2mo,  2  oo 

5 


CIVIL  ENGINEERING. 

BRIDGES    AND    ROOFS.       HYDRAULICS.       MATERIALS   OF   ENGINEERING 
RAILWAY  ENGINEERING. 

Baker's  Engineers'  Surveying  Instruments i2mo,  3  oo 

Bixby's  Graphical  Computing  Table Paper  19^X24*  inches.  25 

**  Burr's  Ancient  and  Modern  Engineering  and  the  Isthmian  Canal.     (Postage, 

27  cents  additional.) 8vo,  3  50 

Comstock's  Field  Astronomy  for  Engineers 8vo,  2  50 

Davis's  Elevation  and  Stadia  Tables 8vo,  i  oo 

Elliott's  Engineering  for  Land  Drainage I2mo,  i  50 

Practical  Farm  Drainage I2mo,  i  oo 

*Fiebeger's  Treatise  on  Civil  Engineering 8vo,  5  oo 

Folwell's  Sewerage.     (Designing  and  Maintenance.) 8vo,  3  oo 

Freitag's  Architectural  Engineering.     2d  Edition,  Rewritten 8vo,  3  50 

French  and  I/es's  Stereotomy 8vo,  2  50 

Goodhue's  Municipal  Improvements I2mo,  i  75 

Goodrich's  Economic  Disposal  of  Towns'  Refuse 8vo,  3  50 

Gore's  Elements  of  Geodesy 8vo,  .2  50 

Hayford's  Text-book  of  Geodetic  Astronomy 8vo,  3  oo 

Bering's  Ready  Reference  Tables  (Conversion  Factors) i6mo,  morocco,  2  50 

Howe's  Retaining  Walls  for  Earth I2mo,  i  25 

Johnson's  (J.  B.)  Theory  and  Practice  of  Surveying Small  8vo,  4  oo 

Johnson's  (L.  J.)  Statics  by  Algebraic  and  Graphic  Methods 8vo,  2  oo 

Laplace's  Philosophical  Essay  on  Probabilities.    (Truscoit  and  Emory.) .  I2mo,  2  oo 

Mahan's  Treatise  on  Civil  Engineering.     (1873.)     (Wood.).  ... 8vo,  5  oo 

*  Descriptive  Geometry 8vo,  i  50 

Merriman's  Elements  of  Precise  Surveying  and  Geodesy Svo,  2  50 

Merriman  and  Brooks's  Handbook  for  Surveyors i6mo,  moro^ .  ~.  oo 

Nugent's  Plane  Surveying 8vo,  3  5^ 

Ogden's  Sewer  Design I2mo,  2  oo 

Patton's  Treatise  on  Civil  Engineering 8vo  half  leather,  7  50 

Reed's  Topographical  Drawing  and  Sketching 4to,  5  oo 

Rideal's  Sewage  and  the  Bacterial  Purification  of  Sewage 8vo,  3  50 

Siebert  and  Biggin's  Modern  Stone-cutting  and  Masonry. 8vo,  i  50 

Smith's  Manual  of  Topographical  Drawing.     (McMillan.) 8vo,  2  50 

Sondericker's  Graphic  Statics,  with  Applications  to  Trusses,  Beams,  and  Arches. 

8vo,  2  oo 

Taylor  and  Thompson's  Treatise  on  Concrete,  Plain  and  Reinforced 8vo,  5  oo 

*  Trautwine's  Civil  Engineer's  Pocket-book i6mo,  morocco,  5  oo 

Wait's  Engineering  and  Architectural  Jurisprudence 8vo,  6  oo 

Sheep,  6  50 

Law  of  Operations  Preliminary  to  Construction  in  Engineering  and  Archi- 
tecture. . 8vo,  5  oo 

Sheep,  5  50 

Law  of  Contracts 8vo,  3  oo 

Warren's  Stereotomy — Problems  in  Stone-cutting 8vo,  2  50 

Webb's  Problems  in  the  Use  and  Adjustment  of  Engineering  Instruments. 

i6mo,  morocco,  i  25 

Wilson's  Topographic  Surveying 8vo,  3  50 


BRIDGES  AND  ROOFS. 

Boiler's  Practical  Treatise  on  the  Construction  of  Iron  Highway  Bridges .  .  8vo,    2  oo 

*       Thames  River  Bridge 4to,  paper,    5  oo 

Burr's  Course  on  the  Stresses  in  Bridges  and  Roof  Trusses,  Arched  Ribs,  and 

Suspension  Bridges 8vo,    3  50 

6 


Burr  and  Falk's  Influence  Lines  for  Bridge  and  Roof  Computations.  . .  .8vo,  3  oo 

Design  and  Construction  of  Metallic  Bridges 8vo,  5  oo 

Du  Bois's  Mechanics  of  Engineering.     Vol.  II Small  4to,  10  oo 

Foster's  Treatise  on  Wooden  Trestle  Bridges 4to,  5  oo 

Fowler's  Ordinary  Foundations 8vo,  3  50 

Greene's  Roof  Trusses 8vo,  i  25 

Bridge  Trusses 8vo,  2  50 

Arches  in  Wood,  Iron,  and  Stone 8vo,  2  50 

Howe's  Treatise  on  Arches 8vo,  4  oo 

Design  of  Simple  Roof-trusses  in  Wood  and  Steel 8vo,  2  oo 

Johnson,  Bryan,  and  Turneaure's  Theory  and  Practice  in  the  Designing  of 

Modern  Framed  Structures Small  4to,  10  oo 

Merriman  and  Jacoby's  Text-book  on  Roofs  and  Bridges: 

Part  I.     Stresses  in  Simple  Trusses 8vo,  2  50 

Part  II.     Graphic  Statics 8vo,  2  50 

Part  III.     Bridge  Design 8vo,  2  50 

Part  IV.     Higher  Structures 8vo,  2  50 

Morison's  Memphis  Bridge 4to,  10  oo 

WaddelFs  De  Pontibus,  a  Pocket-book  for  Bridge  Engineers.  .  i6mo,  morocco,  2  oo 

Specifications  for  Steel  Bridges i2mo,  i  25 

Wright's  Designing  of  Draw-spans.     Two  parts  in  one  volume 8vo,  3  50 


HYDRAULICS. 

Bazin's  Experiments  upon  the  Contraction  of  the  Liquid  Vein  Issuing  from 

an  Orifice.     (Trautwine.) 8vo,  2  oo 

Bovey's  Treatise  on  Hydraulics 8vo,  5  oo 

Church's  Mechanics  of  Engineering 8vo,  6  oo 

Diagrams  of  Mean  Velocity  of  Water  in  Open  Channels paper,  i  50 

Hydraulic  Motors 8vo,  2  oo 

Coffin's  Graphical  Solution  of  Hydraulic  Problems i6mo,  morocco,  2  50 

Flather's  Dynamometers,  and  the  Measurement  of  Power i2mo,  3  oo 

Folwell's  Water-supply  Engineering 8vo,  4  oo 

Frizell's  Water-power • 8vo,  5  oo 

Fuertes's  Water  and  Public  Health i2mo,  i  50 

Water-filtration  Works i2mo,  2  50 

Ganguillet  and  Kutter's  General  Formula  for  the  Uniform  Flow  of  Water  in 

Rivers  and  Other  Channels.     (Hering  and  Trautwine.) 8vo,  4  oo 

Hazen's  Filtration  of  Public  Water-supply 8vo,  3  oo 

Hazlehurst's  Towers  and  Tanks  for  Water-works 8vo,  2  50 

Herschel's  115  Experiments  on  the  Carrying  Capacity  of  Large,  Riveted,  Metal 

Conduits 8vo,  2  oo 

Mason's  Water-supply.     (Considered  Principally  from  a  Sanitary  Standpoint.) 

8vo,  4  oo 

Merriman's  Treatise  on  Hydraulics 8vo,  5  oo 

*  Michie's  Elements  of  Analytical  Mechanics 8vo,  4  oo 

Schuyler's   Reservoirs  for  Irrigation,   Water-power,  and   Domestic   Water- 
supply Large  8vo,  5  oo 

**  Thomas  and  Watt's  Improvement  of  Rivers.     (Post.,  440.  additional. ).4to,  6  oo 

Turneaure  and  Russell's  Public  Water-supplies 8vo,  5  oo 

Wegmann's  Design  and  Construction  of  Dams 4to,  5  oo 

Water-supply  of  the  City  of  New  York  from  1658  to  1895 4to,  10  oo 

Williams  and  Hazen's  Hydraulic  Tables 8vo,  i  50 

Wilson's  Irrigation  Engineering Small  8vo,  4  oo 

Wolff's  Windmill  as  a  Prime  Mover 8vo,  3  oo 

Wood's  Turbines 8vo,  2  50 

Elements  of  Analytical  Mechanics 8vo,  3  oo 

7 


MATERIALS  OF  ENGINEERING. 

Baker's  Treatise  on  Masonry  Construction 8vo,  5  oo 

Roads  and  Pavements 8vo,  5  oo 

Bkck's  United  States  Public  Works ; Oblong  4to,  5  oo 

*  Bovey's  Strength  of  Materials  and  Theory  of  Structures 8vo,  7  50 

Burr's  Elasticity  and  Resistance  of  the  Materials  of  Engineering 8vo,  7  50 

Byrne's  Highway  Construction 8vo,  5  oo 

Inspection  of  the  Materials  and  Workmanship  Employed  in  Construction. 

i6mo,  3  oo 

Church's  Mechanics  of  Engineering 8vo,  6  oo 

Du  Bois's  Mechanics  of  Engineering.     Vol.  I Small  4to,  7  50 

*Eckel's  Cements,  Limes,  and  Plasters 8vo,  6  oo 

Johnson's  Materials  of  Construction Large  8vo,  6  oo 

Fowler's  Ordinary  Foundations 8vo,  3  50 

*  Greene's  Structural  Mechanics , 8vo,  2  50 

Keep's  Cast  Iron 8vo,  2  50 

Lanza's  Applied  Mechanics 8vo,  7  50 

Marten's  Handbook  on  Testing  Materials.     (Henning.)     2  vols 8vo,  7  50 

Maurer's  Technical  Mechanics 8vo,  4  oo 

Merrill's  Stones  for  Building  and  Decoration 8vo,  5  oo 

Merriman's  Mechanics  of  Materials 8vo,  5  oo 

Strength  of  Materials i2mo,  i  oo 

Metcalf's  Steel.     A  Manual  for  Steel-users i2mo,  2  oo 

Patton's  Practical  Treatise  on  Foundations 8vo,  5  oo 

Richardson's  Modern  Asphalt  Pavements.  .  . . 8vo,  3  oo 

Richey's  Handbook  for  Superintendents  of  Construction i6mo,  mor.,  4  oo 

Rockwell's  Roads  and  Pavements  in  France 12010,  i  25 

Sabin's  Industrial  and  Artistic  Technology  of  Paints  and  Varnish 8vo,  3  oo 

Smith's  Materials  of  Machines i2mo,  i  oo 

Snow's  Principal  Species  of  Wood 8vo,  3  50 

Spalding's  Hydraulic  Cement i2mo,  2  oo 

Text-book  on  Roads  and  Pavements i2mo,  2  oo 

Taylor  and  Thompson's  Treatise  on  Concrete,  Plain  and  Reinforced 8vo,  5  oo 

Thurston's  Materials  of  Engineering.     3  Parts 8vo,  8  oo 

Part  I.     Non-metallic  Materials  of  Engineering  and  Metallurgy.  .  ;  .  .8vo,  2  oo 

Part  II.     Iron  and  Steel 8vo,  3  50 

Part  III.     A  Treatise  on  Brasses,  Bronzes,  and  Other  Alloys  and  their 

Constituents 8vo,  2  50 

Thurston's  Text-book  of  the  Materials  of  Construction 8vo,  5  oo 

Tillson's  Street  Pavements  and  Paving  Materials 8vo,  4  oo 

Waddell's  De  Pontibus.    (A  Pocket-book  for  Bridge  Engineers.).  . i6mo,  mor.,  2  oo 

Specifications  for  Steel  Bridges i2mo,  i  25 

Wood's  (De  V.)  Treatise  on  the  Resistance  of  Materials,  and  an  Appendix  on 

the  Preservation  of  Timber 8vo,  2  oo 

Wood's  (De  V.)  Elements  of  Analytical  Mechanics 8vo,  3  oo 

Wood's  (M.  P.)  Rustless  Coatings:    Corrosion  and  Electrolysis  of  Iron  and 

Steel 8vo,  4  oo 


RAILWAY  ENGINEERING. 

Andrew's  Handbook  for  Street  Railway  Engineers 3x5  inches,  morocco,  i  25 

Berg's  Buildings  and  Structures  of  American  Railroads 4to,  5  oo 

Brook's  Handbook  of  Street  Railroad  Location i6mo,  morocco,  I  50 

Butt's  Civil  Engineer's  Field-book i6mo,  morocco,  2  50 

Crandall's  Transition  Curve i6mo,  morocco,  i  50 

Railway  and  Other  Earthwork  Tables 8vo,  i  50 

Dawson's  "Engineering"  and  Electric  Traction  Pocket-book.  .  i6mo,  morocco,  5  oo 

3 


Dredge's  History  of  the  Pennsylvania  Railroad:   (1879) Paper,  5  oo 

*  Drinker's  Tunnelling,  Explosive  Compounds,  and  Rock  Drills. 4to,  half  mor.,  25  oo 

Fisher's  Table  of  Cubic  Yards .- Cardboard,  25 

Godwin's  Railroad  Engineers'  Field-book  and  Explorers'  Guide.  .  .  i6mo,  mor.,  2  50 

Howard's  Transition  Curve  Field-book i6mo,  morocco,  i  50 

Hudson's  Tables  for  Calculating  the  Cubic  Contents  of  Excavations  and  Em- 
bankments  8vo,  i  oo 

Molitor  and  Beard's  Manual  for  Resident  Engineers i6mo,  i  oo 

Nagle's  Field  Manual  for  Railroad  Engineers i6mo,  morocco,  3  oo 

Philbrick's  Field  Manual  for  Engineers i6mo,  morocco,  3  oo 

Searles's  Field  Engineering i6mo,  morocco,  3  oo 

Railroad  Spiral i6mo,  morocco,  i  50 

Taylor's  Prismoidal  Formulae  and  Earthwork 8vo,  i  50 

*  Trautwine's  Method  of  Calculating  the  Cube  Contents  of  Excavations  and 

Embankments  by  the  Aid  of  Diagrams 8vo,  2  oo 

The  Field  Practice  of  Laying  Out  Circular  Curves  for  Railroads. 

1 2 mo,  morocco,  2  50 

Cross-section  Sheet Paper,  25 

Webb's  Railroad  Construction i6mo,  morocco,  5  oo 

Wellington's  Economic  Theory  of  the  Location  of  Railways Small  8vo,  5  oo 


DRAWING. 

Barr's  Kinematics  of  Machinery 8vo,  2  50 

*  Bartlett's  Mechanical  Drawing '. 8vo,  3  oo 

*  "                    "                   "        Abridged  Ed 8vo,  150 

Coolidge's  Manual  of  Drawing 8vo,  paper  i  oo 

Coolidge  and  Freeman's  Elements  of  General  Drafting  for  Mechanical  Engi- 
neers.  Oblong  4to,  2  50 

Durley's  Kinematics  of  Machines 8vo,  4  oo 

Emch's  Introduction  to  Projective  Geometry  and  its  Applications 8vo,  2  50 

Hill's  Text-book  on  Shades  and  Shadows,  and  Perspective 8vo,  2  oo 

Jamison's  Elements  of  Mechanical  Drawing 8vo,  2  50 

Advanced  Mechanical  Drawing 8vo,  2  oo 

Jones's  Machine  Design: 

Part  I.     Kinematics  of  Machinery 8vo,  i  50 

Part  EL.     Form,  Strength,  and  Proportions  of  Parts 8vo,  3  oo 

MacCord's  Elements  of  Descriptive  Geometry 8vo,  3  oo 

Kinematics;  or,  Practical  Mechanism 8vo,  5  oo 

Mechanical  Drawing 4to,  4  oo 

Velocity  Diagrams 8vo,  i  50 

MacLeod's  Descriptive  Geometry Small  8vo,  i  50 

*  Mahan's  Descriptive  Geometry  and  Stone-cutting 8vo,  i  50 

Industrial  Drawing.  (Thompson.) 8vo,  3  50 

Meyer's  Descriptive  Geometry 8vo,  2  oo 

Reed's  Topographical  Drawing  and  Sketching 4to,  5  oo 

Reid's  Course  in  Mechanical  Drawing 8vo,  2  oo 

Text-book  of  Mechanical  Drawing  and  Elementary  Machine  Design. 8vo,  3  oo 

Robinson's  Principles  of  Mechanism 8vo,  3  oo 

Schwamb  and  Merrill's  Elements  of  Mechanism 8vo,  3  co 

Smith's  (R.  S.)  Manual  of  Topographical  Drawing.  (McMillan.) 8vo,  2  50 

Smith  (A.  W.)  and  Marx's  Machine  Design 8vo,  3  oo 

Warren's  Elements  of  Plane  and  Solid  Free-hand  Geometrical  Drawing.  i2mo,  oo 


Drafting  Instruments  and  Operations I2mo, 

Manual  of  Elementary  Projection  Drawing i2mo, 

Manual  of  Elementary  Problems  in  the  Linear  Perspective  of  Form  and 

Shadow i2mo, 

Plane  Problems  in  Elementary  Geometry i2mo, 

9 


Warren's  Primary  Geometry I2mo,  75 

Elements  of  Descriptive  Geometry,  Shadows,  and  Perspective 8vo,  3  50- 

General  Problems  of  Shades  and  Shadows 8vo,  3  oo 

Elements  of  Machine  Construction  and  Drawing 8vo,  7  $a 

Problems,  Theorems,  and  Examples  in  Descriptive  Geometry 8vo,  2  50 

Weisbach's    Kinematics  >md    Power    of    Transmission.        (Hermann    and 

Klein.) : 8vo,  5  oa 

Whelpley's  Practical  Instruction  in  the  Art  of  Letter  Engraving i2mo,  2  oo 

Wilson's  (H.  M.)  Topographic  Surveying 8vo,  3  50 

Wilson's  (V.  T.)  Free-hand  Perspective 8vo,  2  50 

Wilson's  (V.  T.)  Free-hand  Lettering 8vo,  i  oo 

Woolf' s  Elementary  Course  in  Descriptive  Geometry Large  8vo,.  3  oo 

ELECTRICITY  AND  PHYSICS. 

Anthony  and  Brackett's  Text-book  of  Physics.     (Magie.) ~. .  .Small  8vo,  3  oo 

Anthony's  Lecture-notes  on  the  Theory  of  Electrical  Measurements.  . .  .  i2mo,  i  oo 

Benjamin's  History  of  Electricity 8vo,  3  oo 

Voltaic  Cell 8vo,  3  oo 

Classen's  Quantitative  Chemical  Analysis  by  Electrolysis.     (Boltwood.).8vo,  3  oo 

Crehore  and  Squier's  Polarizing  Photo-chronograph 8vo,  3  oo 

Dawson's  "Engineering"  and  Electric  Traction  Pocket-book.  i6mo,  morocco,  5  oo 
Dolezalek's    Theory   of   the    Lead   Accumulator    (Storage    Battery).      (Von 

Ende.) I2mo,  2  50 

Duhem's  Thermodynamics  and  Chemistry.     (Burgess.) 8vo,  4  oo 

Flather's  Dynamometers,  and  the  Measurement  of  Power i2mo,  3  oo 

Gilbert's  De  Magnete.     (Mottelay.) 8vo,  2  50 

Hanchett's  Alternating  Currents  Explained I2mo,  i  oo 

Bering's  Ready  Reference  Tables  (Conversion  Factors) i6mo,  morocco,  2  50 

Holman's  Precision  of  Measurements 8vo,  2  oo 

Telescopic   Mirror-scale  Method,  Adjustments,  and  Tests.  . .  .Large  8vo,  75 

Xinzbrunner's  Testing  of  Continuous-current  Machines 8vo,  2  oo 

Landauer's  Spectrum  Analysis.     (Tingle.) 8vo,  3  oo 

Le  Chateliers  High-temperature  Measurements.  (Boudouard — Burgess.)  i2mo,  3  oo 

Lob's  Electrochemistry  of  Organic  Compounds.     (Lorenz.) 8vo,  3  oo 

*  Lyons's  Treatise  on  Electromagnetic  Phenomena.   Vols.  I.  and. II.  8vo,  each,  6  oo 

*  Michie's  Elements  of  Wave  Motion  Relating  to  Sound  and  Light 8vo,  4  oo 

Niaudet's  Elementary  Treatise  on  Electric  Batteries.     (Fishback.) i2mo,  2  50 

*  Rosenberg's  Electrical  Engineering.     (Haldane  Gee — Kinzbrunner.).  .  .8vo,  i  50 

Ryan,  Norris,  and  Hoxie's  Electrical  Machinery.     Vol.  1 8vo,  2  50 

Thurston's  Stationary  Steam-engines 8vo,  2  50 

*  Tillman's  Elementary  Lessons  in  Heat 8vo,  i  50 

Tory  and  Pitcher's  Manual  of  Laboratory  Physics Small  8vo,  2  oo 

Ulke's  Modern  Electrolytic  Copper  Refining 8vo,  3  oo 

LAW. 

*  Davis's  Elements  of  Law 8vo,  2  50 

*  Treatise  on  the  Military  Law  of  United  States 8vo,  7  oo 

*  Sheep,  7  50 

Manual  for  Courts-martial i6mo,  morocco,  i  50 

Wait's  Engineering  and  Architectural  Jurisprudence 8vo ,  6  oo 

Sheep,  6  50 

Law  of  Operations  Preliminary  to  Construction  in  Engineering  and  Archi- 
tecture  8vo  5  oo 

Sheep,  5  50 

Law  of  Contracts 8vo,  3  oo 

Winthrop's  Abridgment  of  Military  Law I2mo»  2  So 

10 


MANUFACTURES. 

Bernadou's  Smokeless  Powder— Nitro-cellulose  and  Theory  of  the  Cellulose 

Molecule i2mo,  2  50 

Holland's  Iron  Founder i2mo,  2  50 

"  The  Iron  Founder,"  Supplement 1203.0,  2  50 

Encyclopedia  of  Founding  and  Dictionary  of  Foundry  Terms  Used  in  the 

Practice  of  Moulding I2mo,  3  oo 

Eissler's  Modern  High  Explosives 8vo,  4  oo 

Eff rent's  Enzymes  and  their  Applications.     (Prescott.) 8vo,  3  oo 

Fitzgerald's  Boston  Machinist i2mo,  i  oo 

Ford's  Boiler  Making  for  Boiler  Makers i8mo,  i  oo 

Hopkin's  Oil-chemists'  Handbook 8vo,  3  oo 

Keep's  Cast  Iron 8vo,  2  50 

Leach's  The  Inspection  and  Analysis  of  Food  with  Special  Reference  to  State 

Control Large  8vo,  7  50 

Matthews's  The  Textile  Fibres 8vo,  3  50 

Metcalf's  Steel.     A  Manual  for  Steel-users 12 mo,  2  oo 

Metcalfe's  Cost  of  Manufactures — And  the  Administration  of  Workshops.  8vo,  5  oo 

Meyer's  Modern  Locomotive  Construction 4to,  10  oo 

Morse's  Calculations  used  in  Cane-sugar  Factories i6mo,  morocco,    i  50 

*  Reisig's  Guide  to  Piece-dyeing 8vo,  25  oo 

Sabin's  Industrial  and  Artistic  Technology  of  Paints  and  Varnish.  ... 8vo,  3  oo 

Smith's  Press-working  of  Metals 8vo,  3  oo 

Spalding's  Hydraulic  Cement I2mo,  2  oo 

Spencer's  Handbook  for  Chemists  of  Beet-sugar  Houses i6mo,  morocco,  3  oo 

Handbook  for  Cane  Sugar  Manufacturers i6mo,  morocco,  3  oo 

Taylor  and  Thompson's  Treatise  on  Concrete,  Plain  and  Reinforced 8vo,  5  oo 

Thurston's  Manual  of  Steam-boilers,  their  Designs,  Construction  and  Opera- 
tion  8vo,  5  oo 

*  Walke's  Lectures  on  Explosives 8vo,  4  oo 

Ware's  Beet-sugar  Manufacture  and  Refining Small  8vo,  4  oo 

West's  American  Foundry  Practice i2mo,  2  50 

Moulder's  Text-book i2mo,  2  50 

Wolff's  Windmill  as  a  Prime  Mover 8vo,  3  oo 

Wood's  Rustless  Coatings:  Corrosion  and  Electrolysis  of  Iron  and  Steel.  .8vo,  4  oo 


MATHEMATICS. 

Baker's  Elliptic  Functions 8vo,  I  50 

*  Bass's  Elements  of  Differential  Calculus i2mo,  4  oo 

Briggs's  Elements  of  Plane  Analytic  Geometry I2mo,  i  oo 

Compton's  Manual  of  Logarithmic  Computations 12 mo,  i  50 

Davis's  Introduction  to  the  Logic  of  Algebra 8vo,  i  50 

*  Dickson's  College  Algebra Large  i2mo,  i  50 

*  Introduction  to  the  Theory  of  Algebraic  Equations Large  I2mo,  i  25 

Emch's  Introduction  to  Projective  Geometry  and  its  Applications 8vo,  2  50 

Halsted's  Elements  of  Geometry 8vo,  i  75 

Elementary  Synthetic  Geometry 8vo,  I  50 

Rational  Geometry I2mo,  i  75 

*  Johnson's  (J.  B.)  Three-place  Logarithmic  Tables:  Vest-pocket  size. paper,  15 

100  copies  for  5  oo 

*  Mounted  on  heavy  cardboard,  8  X  TO  inches,  25 

10  copies  for  2  OO 

Johnson's  (W.  W.)  Elementary  Treatise  on  Differential  Calculus.  .Small  8vo,  3  oo 

Johnson's  (W.  W.)  Elementary  Treatise  on  the  Integral  Calculus .  Small  8vo,  i  50 

11 


Johnson's  (W.  W.)  Curve  Tracing  in  Cartesian  Co-ordinates i2mo,     i  oo 

Johnson's  (W.  'W.)  Treatise  on  Ordinary  and  Partial  Differential  Equations. 

Small  8vo,    3  50 
Johnson's  (W.  W.)  Theory  of  Errors  and  the  Method  of  Least  Squares.  i2mo,     i  50 

*  Johnson's  (W.  W.)  Theoretical  Mechanics i2mo,    3  oo 

Laplace's  Philosophical  Essay  on  Probabilities.    (Truscott  and  Emory.) .  i2mo,    2  oo 

*  Ludlow  and  Bass.     Elements  of  Trigonometry  and  Logarithmic  and  Other 

Tables 8vo,    3  oo 

Trigonometry  and  Tables  published  separately Each,    2  oo 

*  Ludlow's  Logarithmic  and  Trigonometric  Tables 8vo,    i  oo 

Mathematical  Monographs.     Edited  by  Mansfield  Merriman  and  Robert 

S.  Woodward Octavo,  each     i  oo 

No.  i.  History  of  Modern  Mathematics,  by  David  Eugene  Smith. 
No.  2.  Synthetic  Projective  Geometry,  by  George  Bruce  Halsted. 
No.  3.  Determinants,  by  Laenas  Gifford  Weld.  No.  4.  Hyper- 
bolic Functions,  by  James  McMahon.  No.  5.  Harmonic  Func- 
tions, by  William  E.  Byerly.  No.  6.  Grassmann's  Space  Analysis, 
by  Edward  W.  Hyde.  No.  7.  Probability  and  Theory  of  Errors, 
by  Robert  S.  Woodward.  No.  8.  Vector  Analysis  and  Quaternions, 
by  Alexander  Macfarlane.  No.  9.  Differential  Equations,  by 
William  Woolsey  Johnson.  No.  10.  The  Solution  of  Equations, 
byj  Mansfield  Merriman.  No.  1 1.  Functions  of  a  Complex  Variable, 
by  Thomas  S.  Fiske. 

Maurer's  Technical  Mechanics 8vo,    4  oo 

Merriman  and  Woodward's  Higher  Mathematics 8vo,    5  oo 

Merriman's  Method  of  Least  Squares 8vo,    2  oo 

Rice  and  Johnson's  Elementary  Treatise  on  the  Differential  Calculus. .  Sm.  8vo,    3  oo 

Differential  and  Integral  Calculus.     2  vols.  in  one Small  8vo,    2  50 

Wood's  Elements  of  Co-ordinate  Geometry. 8vo,    2  oo 

Trigonometry:  Analytical,  Plane,  and  Spherical i2mo,    i  oo 


MECHANICAL  ENGINEERING. 
MATERIALS  OF  ENGINEERING,  STEAM-ENGINES  AND  BOILERS. 

Bacon's  Forge  Practice i2mo,  i  50 

Baldwin's  Steam  Heating  for  Buildings I2mo,  2  50 

Barr's  Kinematics  of  Machinery 8vo,  2  50 

*  Bartlett's  Mechanical  Drawing 8vo,  3  oo 

*  "                                   "        Abridged  Ed 8vo,  150 

Benjamin's  Wrinkles  and  Recipes i2mo,  2  oo 

Carpenter's  Experimental  Engineering 8vo,  6  oo 

Heating  and  Ventilating  Buildings 8vo,  4  oo 

Gary's  Smoke  Suppression  in  Plants  using  Bituminous  CoaL     (In  Prepara- 
tion.) 

Clerk's  Gas  and  Oil  Engine Small  8vo,  4  oo 

Coolidge's  Manual  of  Drawing 8vo,  paper,  i  oo 

Coelidge  and  Freeman's  Elements  of  General  Drafting  for  Mechanical  En- 
gineers  Oblong  4to,  2  50 

Cromwell's  Treatise  on  Toothed  Gearing i2mo,  i  50 

Treatise  on  Belts  and  Pulleys i2mo,  i  50 

Durley's  Kinematics  of  Machines 8vo,  4  oo 

Flather's  Dynamometers  and  the  Measurement  of  Power 121110,  3  oo 

Rope  Driving i2mo,  2  oo 

Gill's  Gas  and  Fuel  Analysis  for  Engineers i2mo,  i  25 

Hall's  Car  Lubrication i2mo,  i  oo 

Bering's  Ready  Reference  Tables  (Conversion  Factors) i6mo,  morocco,  2  50 

12 


Button's  The  Gas  Engine 8vo,  5  oo 

Jamison's  Mechanical  Drawing 8vo,  2  50 

Jones's  Machine  Design: 

Part  I.     Kinematics  of  Machinery 8vo,  i  50 

Part  II.     Form,  Strength,  and  Proportions  of  Parts 8vo,  3  oo 

Kent's  Mechanical  Engineers'  Pocket-book i6mo,  morocco,  5  oo 

Kerr's  Power  and  Power  Transmission 8vo,  2  oo 

Leonard's  Machine  Shop,  Tools,  and  Methods 8vo,  4  oo 

*  Lorenz's  Modern  Refrigerating  Machinery.    (Pope,  Haven,  and  Dean.) .  . 8vo,  4  oo 

MacCord's  Kinematics;  or,  Practical  Mechanism 8vo,  5  oo 

Mechanical  Drawing 4to,  4  oo 

Velocity  Diagrams ' 8vo,  i  50 

MacFar land's  Standard  Reduction  Factors  for  Gases 8vo,  i  50 

Mahan's  Industrial  Drawing.     (Thompson.) 8vo,  3  50 

Poole's  Calorific  Power  of  Fuels 8vo,  3  oo 

Reid's  Course  in  Mechanical  Drawing 8vo,  2  oo 

Text-book  of  Mechanical  Drawing  and  Elementary  Machine  Design. 8 vo,  3  oo 

Richard's  Compressed  Air i2mo,  i  50 

Robinson's  Principles  of  Mechanism 8vo,  3  oo 

Schwamb  and  Merrill's  Elements  of  Mechanism 8vo,  3  oo 

Smith's  (O.)  Press-working  of  Metals. 8vo,  3  oo 

Smith  (A.  W.)  and  Marx's  Machine  Design 8vo,  3  oo 

Thurston's   Treatise   on   Friction  and   Lost   Work  in   Machinery  and   Mill 

Work 8vo,  3  oo 

Animal  as  a  Machine  and  Prime  Motor,  and  the  Laws  of  Energetics.  1 2mo,  i  oo 

Warren's  Elements  of  Machine  Construction  and  Drawing 8vo,  7  50 

Weisbach's    Kinematics    and    the    Power   of   Transmission.     (Herrmann — 

Klein.) 8vo,  5  oo 

Machinery  of  Transmission  and  Governors.     (Herrmann — Klein.).  .8 vo,  500 

Wolff's  Windmill  as  a  Prime  Mover 8vo,  3  oo 

Wood's  Turbines, 8vo,  2  50 


MATERIALS  OP  ENGINEERING. 

*  Bovey's  Strength  of  Materials  and  Theory  of  Structures 8vo,  7  50 

Burr's  Elasticity  and  Resistance  of  the  Materials  of  Engineering.    6th  Edition. 

Reset 8vo,  7  50 

Church's  Mechanics  of  Engineering 8vo,  6  oo 

*  Greene's  Structural  Mechanics 8vo,  2  50 

Johnson's  Materials  of  Construction 8vo,  6  oo 

Keep's  Cast  Iron 8vo,  2  50 

lanza's  Applied  Mechanics 8vo,  7  50 

Martens's  Handbook  on  Testing  Materials.     (Henning.) 8vo,  7  50 

Maurer's  Technical  Mechanics 8vo,  4  oo 

Merriman's  Mechanics  of  Materials 8vo,  5  oo 

Strength  of  Materials I2mo,  i  oo 

Metcalf's  Steel.     A  manual  for  Steel-users i2mo,  2  oo 

Sabin's  Industrial  and  Artistic  Technology  of  Paints  and  Varnish 8vo,  3  oo 

Smith's  Materials  of  Machines.  . .- i2mo,  i  oo 

Thurston's  Materials  of  Engineering 3  vols.,  8vo,  8  oo 

Part  II.     Iron  and  Steel 8vo,  3  50 

Part  III.     A  Treatise  on  Brasses,  Bronzes,  and  Other  Alloys  and  their 

Constituents 8vo,  2  50 

Text-book  of  the  Materials  of  Construction 8vo,  5  oo 

Wood's  (De  V.)  Treatise  on  the  Resistance  of  Materials  arid  an  Appendix  on 

the  Preservation  of  Timber 8vo,  2  oo 

13 


Wood's  (De  V.)  Elements  of  Analytical  Mechanics 8vo,  3  oo 

Wood's  (M.  P.)  Rustless  Coatings:    Corrosion  and  Electrolysis  of  Iron  and 

Steel 8vo,  4  oo 

STEAM-ENGINES  AND  BOILERS. 

Berry's  Temperature-entropy  Diagram izmo,  i  25 

Carnot's  Reflections  on  the  Motive  Power  of  Heat.     (Thurston.) i2mo,  I  50 

Dawson's  "Engineering"  and  Electric  Traction  Pocket-book.  .      i6mo,  mor.,  5  oo 

Ford's  Boiler  Making  for  Boiler  Makers i8mo,  i  oo 

Goss's  Locomotive  Sparks 8vo,  2  oo 

Hemenway's  Indicator  Practice  and  Steam-engine  Economy i2mo,  2  oo 

Button's  Mechanical  Engineering  of  Power  Plants 8vo,  5  oo 

Heat  and  Heat-engines 8vo,  5  oo 

Kent's  Steam  boiler  Economy 8vo,  4  oo 

Kneass's  Practice  and  Theory  of  the  Injector 8vo,  i  50 

MacCord's  Slide-valves 8vo,  2  oo 

Meyer's  Modern  Locomotive  Construction 4to,  10  oo 

Peabody's  Manual  of  the  Steam-engine  Indicator I2mo,  i  50 

Tables  of  the  Properties  of  Saturated  Steam  and  Other  Vapors   8vo,  i  oo 

Thermodynamics  of  the  Steam-engine  and  Other  Heat-engines 8vo,  5  oo 

Valve-gears  for  Steam-engines. 8vo,  2  50 

Peabody  and  Miller's  Steam-boilers 8vo,  4  oo 

Pray's  Twenty  Years  with  the  Indicator Large  8vo,  2  50 

Pupin's  Thermodynamics  of  Reversible  Cycles  in  Gases  and  Saturated  Vapors. 

(Osterberg.) I2mo,  i  25 

Reagan's  Locomotives:  Simple   Compound,  and  Electric 12 mo,  2  50 

Rontgen's  Principles  of  Thermodynamics.     (Du  Bois.) 8vo,  5  oo 

Sinclair's  Locomotive  Engine  Running  and  Management i2mo,  2  oo 

Smart's  Handbook  of  Engineering  Laboratory  Practice .  .i2mo,  2  50 

Snow's  Steam-boiler  Practice 8vo,  3  oo 

Spangler's  Valve-gears 8vo,  2  50 

Notes  on  Thermodynamics i2mo,  i  oo 

Spangler,  Greene,  and  Marshall's  Elements  of  Steam-engineering 8vo,  3  oo 

Thurston's  Handy  Tables 8vo,  i  50 

Manual  of  the  Steam-engine 2  vols.,  8vo,  10  oo 

Part  I.     History,  Structure,  and  Theory 8vo,  6  oo 

Part  II.     Design,  Construction,  and  Operation. 8vo,  6  oo 

Handbook  of  Engine  and  Boiler  Trials,  and  the  Use  of  the  Indicator  and 

the  Prony  Brake 8vo,  5  oo 

Stationary  Steam-engines 8vo,  2  50 

Steam-boiler  Explosions  in  Theory  and  in  Practice I2mo,  i  50 

Manual  of  Steam-boilers,  their  Designs,  Construction,  and  Operation 8vo,  5  oo 

Weisbach's  Heat,  Steam,  and  Steam-engines.     (Du  Bois.) 8vo,  5  oo 

Whitham's  Steam-engine  Design 8vo,  5  oo 

Wilson's  Treatise  on  Steam-boilers.     (Flather.) i6mo,  2  50 

Wood's  Thermodynamics,  Heat  Motors,  and  Refrigerating  Machines.  .  .8vo,  4  oo 


MECHANICS  AND  MACHINERY. 

Barr's  Kinematics  of  Machinery 8vo,  2  50 

*  Bovey's  Strength  of  Materials  and  Theory  of  Structures   8vo,  7  50 

Chase's  The  Art  of  Pattern-making I2mo,  2  50 

Church's  Mechanics  of  Engineering 8vo,  6  oo 

Notes  and  Examples  in  Mechanics 8vo,  2  oo 

Compton's  First  Lessons  in  Metal- working i2mo,  i  50 

Compton  and  De  Groodt's  The  Speed  Lathe i2mo,  i  50 

14 


Cromwell's  Treatise  on  Toothed  Gearing I2mo,  I  50 

Treatise  on  Belts  and  Pulleys i2mo,  i  50 

Dana's  Text-book  of  Elementary  Mechanics  for  Colleges  and  Schools.  .i2mo,  i  50 

Dingey's  Machinery  Pattern  Making i2mo,  2  oo 

Dredge's  Record  of  the  Transportation  Exhibits  Building  of  the  World's 

Columbian  Exposition  of  1893 4to  half  morocco,  5  oo 

Du  Bois's  Elementary  Principles  of  Mechanics: 

Vol.      I.     Kinematics 8vo,  3  50 

Vol.    II.     Statics 8vo,  4  oo 

Mechanics  of  Engineering.     Vol.    I Small  4to,  7  50 

VoL  II Small  4to,  10  oo 

Durley's  Kinematics  of  Machines 8vo,  4  oo 

Fitzgerald's  Boston  Machinist i6mo,  i  oo 

Flather's  Dynamometers,  and  the  Measurement  of  Power I2mo,  3  oo 

Rope  Driving i2mo,  2  oo 

Goss's  Locomotive  Sparks 8vo,  2  oo 

*  Greene's  Structural  Mechanics 8vo,  2  50 

Hall's  Car  Lubrication i2mo,  i  oo 

Holly's  Art  of  Saw  Filing i8mo,  75 

James's  Kinematics  of  a  Point  and  the  Rational  Mechanics  of  a  Particle. 

Small  8vo,  2  oo 

*  Johnson's  (W.  W.)  Theoretical  Mechanics i2mo,  3  oo 

Johnson's  (L.  J.)  Statics  by  Graphic  and  Algebraic  Methods 8vo,  2  oo 

Jones's  Machine  Design: 

Part    I.     Kinematics  of  Machinery 8vo,  i  50 

Part  II.     Form,  Strength,  and  Proportions  of  Parts 8vo,  3  oo 

Kerr's  Power  and  Power  Transmission 8vo,  2  oo 

Lanza's  Applied  Mechanics 8vo,  7  50 

Leonard's  Machine  Shop,  Tools,  and  Methods 8vo,  4  oo 

*  Lorenz's  Modern  Refrigerating  Machinery.     (Pope,  Haven,  and  Dean.). 8vo,  4  oo 
MacCord's  Kinematics;  or,  Practical  Mechanism 8vo,  5  oo 

Velocity  Diagrams 8vo,  i  50 

Maurer's  Technical  Mechanics 8vo,  4  oo 

Merriman's  Mechanics  of  Materials . 8vo,  5  oo 

*  Elements  of  Mechanics I2mo,  i  oo 

*  Michie's  Elements  of  Analytical  Mechanics 8vo,  4  oo 

Reagan's  Locomotives:   Simple,  Compound,  and  Electric i2mo,  2  50 

Reid's  Course  in  Mechanical  Drawing 8vo,  2  oo 

Text-book  of  Mechanical  Drawing  and  Elementary  Machine  Design. 8vo,  3  oo 

Richards's  Compressed  Air i2mo,  i  50 

Robinson's  Principles  of  Mechanism 8vo,  3  oo 

Ryan,  Norris,  and  Hoxie's  Electrical  Machinery.     Vol.  1 8vo,  2  50 

Schwamb  and  Merrill's  Elements  of  Mechanism 8vo,  3  oo 

Sinclair's  Locomotive-engine  Running  and  Management. . i2mo,  2  oo 

Smith's  (O.)  Press-working  of  Metals 8vo,  3  oo 

Smith's  (A.  W.)  Materials  of  Machines I2mo,  i  oo 

Smith  (A.  W.)  and  Marx's  Machine  Design 8vo,  3  oo 

Spangler,  Greene,  and  Marshall's  Elements  of  Steam-engineering 8vo,  3  oo 

Thurston's  Treatise  on  Friction  and  Lost  Work  in    Machinery  and    Mill 

Work 8vo,  3  oo 

Animal  as  a  Machine  and  Prime  Motor,  and  the  Laws  of  Energetics. 

I2mo,  i  oo 

Warren's  Elements  of  Machine  Construction  and  Drawing 8vo,  7  50 

Weisbach's  Kinematics  and  Power  of  Transmission.   (Herrmann — Klein.) .  8vo,  5  oo 

Machinery  of  Transmission  and  Governors.      (Herrmann — Klein. ).8vo,  5  oo 

Wood's  Elements  of  Analytical  Mechanics 8vo,  3  oo 

Principles  of  Elementary  Mechanics i2mo,  i  25 

Turbines 8vo,  2  50 

The  World's  Columbian  Exposition  of  1893 4to,  i  oo 

,      15 


METALLURGY. 

Egleston's  Metallurgy  of  Silver,  Gold,  and  Mercury: 

Vol.    I.     Silver 8vo,  7  50 

Vol.  II.     Gold  and  Mercury 8vo,  7  50 

**  Iles's  Lead-smelting.     (Postage  9  cents  additional.) i2mo,  2  50 

Keep's  Cast  Iron .8vo,  2  50 

Kunhardt's  Practice  of  Ore  Dressing  in  Europe 8vo,  i  50 

Le  Chatelier's  High-temperature  Measurements.  (Boudouard — Burgess. )i2mo.  3  oo 

Metcalf's  Steel.     A  Manual  for  Steel-users i2mo,  2  oo 

Minet's  Production  of  Aluminum  and  its  Industrial  Use.     (Waldo.). ..  .  I2mo,  2  50 

Robine  and  Lenglen's  Cyanide  Industry.     (Le  Clerc.) 8vo, 

Smith's  Materials  of  Machines I2mo,  i  oo 

Thurston's  Materials  of  Engineering.     In  Three  Parts 8vo,  8  oo 

Part    II.     Iron  and  Steel 8vo,  3  50 

Part  III.     A  Treatise  on  Brasses,  Bronzes,  and  Other  Alloys  and  their 

Constituents 8vo,  2  50 

Ulke's  Modern  Electrolytic  Copper  Refining 8vo,  3  oo 


MINERALOGY. 

Barringer's  Description  of  Minerals  of  Commercial  Value.    Oblong,  morocco,  2  50 

Boyd's  Resources  of  Southwest  Virginia 8vo,  3  oo 

Map  of  Southwest  Virignia Pocket-book  form.  2  oo 

Brush's  Manual  of  Determinative  Mineralogy.     (Penfield.) 8vo,  4  oo 

Chester's  Catalogue  of  Minerals 8vo,  paper,  i  oo 

Cloth,  i  25 

Dictionary  of  the  Names  of  Minerals 8vo,  3  50 

Dana's  System  of  Mineralogy Large  8vo,  half  leather,  12  50 

First  Appendix  to  Dana's  New  "  System  of  Mineralogy." Large  8vo,  i  oo 

Text-book  of  Mineralogy 8vo,  4  oo 

Minerals  and  How  to  Study  Them i2mo.  i  50 

Catalogue  of  American  Localities  of  Minerals Large  8vo,  i  oo 

Manual  of  Mineralogy  and  Petrography i2mo,  2  oo 

Douglas's  Untechnical  Addresses  on  Technical  Subjects , .  i2mo,  i  oo 

Eakle's  Mineral  Tables 8vo,  i  25 

Egleston's  Catalogue  of  Minerals  and  Synonyms 8vo,  2  50 

Hussak's  The  Determination  of  Rock-forming  Minerals.    ( Smith.). Small 8vo,  2  oo 

Merrill's  Non-metallic  Minerals:  Their  Occurrence  and  Uses 8vo,  4  oo 

*  Penfield's  Notes  on  Determinative  Mineralogy  and  Record  of  Mineral  Tests. 

8vo,  paper,  50 
Rosenbusch's   Microscopical  Physiography   of   the   Rock-making  Minerals. 

(Iddings.) 8vo,  5  oo 

*  Tillman's  Text-book  of  Important  Minerals  and  Rocks 8vo,  2  oo 


MINING. 

Beard's  Ventilation  of  Mines i2mo,  2  50 

Boyd's  Resources  of  Southwest  Virginia 8vo,  3  oo 

.  Map  of  Southwest  Virginia Pocket-book  form,  2  oo 

Douglas's  Untechnical  Addresses  on  Technical  Subjects i2mo,  i  oo 

*  Drinker's  Tunneling,  Explosive  Compounds,  and  Rock  Drills.  -4to,hf.  mor.,  25  oo 

Eissler's  Modern  High  Explosives 8vo,  4  oo 

16 


Fowler's  Sewage  Works  Analyses i2mo,  2  oo 

Goodyear's  Coal-mines  of  the  Western  Coast  of  the  United  States i2mo,  2  50 

Ihlseng's  Manual  of  Mining 8vo,  5  oo 

**  lles's  Lead-smelting.     (Postage  QC.  additional.) I2mo,  2  50 

Kunhardt's  Practice  of  Ore  Dressing  in  Europe 8vo,  i  50 

O'Driscoll's  Notes  on  the  'Treatment  of  Gold  Ores 8vo,  2  oo 

Robine  and  Lenglen's  Cyanide  Industry.     (Le  Clerc.) 8vo, 

*  Walke's  Lectures  on  Explosives 8vo,  4  oo 

Wilson's  Cyanide  Processes ; i2mo,  i  50 

Chlorination  Process '.....  i i2mo,  i  50 

Hydraulic  and  Placer  Mining i2mo,  2  oo 

Treatise  on  Practical  and  Theoretical  Mine  Ventilation i2mo,  i  25 


SANITARY  SCIENCE. 

Bashore's  Sanitation  of  a  Country  House i2mo,  i  op 

Folwell's  Sewerage.     (Designing,  Construction,  and  Maintenance.) 8vo,  3  oo 

Water-supply  Engineering 8vo,  4  oo 

Fuertes's  Water  and  Public  Health i2mo,  i  50 

Water-filtration  Works I2mo,  2  50 

Gerhard's  Guide  to  Sanitary  House-inspection i6mo,  i  oo 

Goodrich's  Economic  Disposal  of  Town's  Refuse Demy  8vo,  3  50 

Hazen's  Filtration  of  Public  Water-supplies 8vo,  3  oo 

Leach's  The  Inspection  and  Analysis  of  Food  with  Special  Reference  to  State 

Control 8vo,  7  50 

Mason's  Water-supply.  (Considered  principally  from  a  Sanitary  Standpoint)  8vo,  4  oo 

Examination  of  Water.     (Chemical  and  Bacteriological.) i2mo,  i  25 

Ogden's  Sewer  Design i2mo,  2  oo 

Prescott  and  Winslow's  Elements  of  Water  Bacteriology,  with  Special  Refer- 
ence to  Sanitary  Water  Analysis i2mo,  i  25 

*  Price's  Handbook  on  Sanitation : I2mo,  j  50 

Richards's  Cost  ot  Food.     A  Study  in  Dietaries i2mo,  i  oo 

Cost  of  Living  as  Modified  by  Sanitary  Science I2mo,  i  oo 

Richards  and  Woodman's  Air.  Water,  and  Food  from  a  Sanitary  Stand- 
point  8vo,  2  oo 

*  Richards  and  Williams's  The  Dietary  Computer 8vo,  i  50 

Rideal's  Sewage  and  Bacterial  Purification  of  Sewage .8vo,  3  50 

Turneaure  and  Russell's  Public  Water-supplies 8vo,  5  oo 

Von  Behring's  Suppression  of  Tuberculosis.     (Bolduan.)  . i2mo,  i  oo 

Whipple's  Microscopy  of  Drinking-water 8vo,  3  50 

Winton's  Microscopy  of  Vegetable  Foods 8vo,  7  50 

Woodhull's  Notes  on  Military  Hygiene i6mo,  x  50 


MISCELLANEOUS. 

De  Fursac's  Manual  of  Psychiatry.     (Rosanoff  and  Collins.) Large  I2mo,  2  50 

Emmons's  Geological  Guide-book  of  the  Rocky  Mountain  Excursion  of  the 

International  Congress  of  Geologists Large  8vo,  i  50 

Ferrel's  Popular  Treatise  on  the  Winds . .  •. 8vo,  4  oo 

Haines's  American  Railway  Management I2mo,  2  50 

Mott's  Fallacy  of  the  Present  Theory  of  Sound i6mo,  I  oo 

Ricketts's  History  of  Rensselaer  Polytechnic  Institute,  1824-1 894.. Small  8vo,  3  oo 

Rostoski's-Serum  Diagnosis.     (Bolduan.) I2mo,  i  oo 

Rotherham's  Emphasized  New  Testament Large  8vo,  2  oo 

17 


Steel's  Treatise  on  the  Diseases  of  the  Dog 8vo,  3  50 

The  World's  Columbian  Exposition  of  1893 4to,  i  oo 

Von  Behring's  Suppression  ot  Tuberculosis.     (Bolduan.) i2mo,  i  oo 

Winslow's  Elements  of  Applied  Microscopy i2mo,  i  50 

Worcester  and  Atkinson.     Small  Hospitals,  Establishment  and  Maintenance; 

Suggestions  for  Hospital  Architecture :  Plans  for  Small  Hospital .  1 2mo ,  i  25 


HEBREW  AND  CHALDEE  TEXT-BOOKS. 

Green's  Elementary  Hebrew  Grammar I2mo,  i  25 

Hebrew  Chrestomathy 8vo,  2  oo 

Gesenius's  Hebrew  and  Chaldee  Lexicon  to  the  Old  Testament  Scriptures. 

(Tregelles.) Small  4to,  half  morocco,  5  oo 

Letteris's  Hebrew  Bible 8vo,  2  25 

18 


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